CN1835420B - Optical performance monitor - Google Patents

Abstract

An optical performance monitor for accurate monitoring of the OSNR of a WDM optical signal is provided wherein a demultiplexing arrayed waveguide grating (AWG) having a plurality of Vernier input ports is disposed between an optical switch and a photodiode array coupled to the output ports of the AWG. In operation, the optical switch sequentially provides the input optical signal into each of the Vernier ports, and signals detected by photodiodes are stored in a memory unit. The apparatus is capable of monitoring the OSNR of the WDM signal with a frequency step which is M times smaller than a frequency spacing between the AWG transmission bands, while enabling the OSNR monitoring in an enhanced dynamic range by providing accurate noise sampling.

Description

Optical performance monitor

The cross reference of related application

The U.S. Provisional Patent Application of " OSNR is measured ... " by name that the present invention advocates to submit on March 11st, 2005 number is 60/660; 982 priority; And the present invention is that the Patent Application No. of " optical performance monitor " by name submitted on July 22nd, 2004 is 10/896779 continuation application; This patent application advocates that the Patent Application No. of submitting on July 23rd, 2003 is 60/489; 545 priority merges among the present invention through the full content of reference with them at this.

Technical field

The present invention relates to be used for the optical performance monitor of optical communication, particularly relate to a kind of method and apparatus of multichannel that be used for accurately monitoring via the OSNR (OSNR) of wavelength division multiplexing (WDM) channel of optical medium propagation.

Background of invention

The light communication system of using wavelength division multiplexing (WDM) technology is typically less than the spacing of 1 nanometer (nm) through as far as possible little channel separation, realizes big capacity information transmission.When the spacing of channel was dwindled, the spectrum signature of monitoring and controlling channels had more importantly meaning at aspects such as checking system function, recognition performance drift and shielding system faults.For instance, when surveying wave length shift, this monitoring is just very necessary, because wave length shift is easy to cause signal to transit to another optical channel from an optical channel.Simultaneously, in order to ensure image intensifer operate as normal commonly used in the network, it also is very important that wavelength parameter is fed back to network element (network element) in real time.

As everyone knows, in the art, be used for measuring optical instrument, be called as optical spectra analyzer (OSAs, spectrometer) as the luminous power of the function of wavelength.In order to confirm unique spectral component, most of traditional spectrometers (OSA) adopt the optical filter of tunable wave length, for example Fabry-Perot (Fabry-Perot) interferometer or diffraction grating (Diffraction Grating).Under latter event, light is to reflect out from diffraction grating with the proportional angle of wavelength; Utilize the wave detector array then, based on light by the angle analysis spectrum of diffraction.Perhaps, diffraction light is seen through slit, detect by a little detector then.

The laboratory equipment of traditional spectrometer (OSAs) work of being designed under laboratory environment, in order to ensure the wavelength of this equipment and power accurately, need carry out the verification of complicacy at any time to wavelength and luminous power.And these install not only bulky usually but also cost an arm and a leg.

Light communication system needs the optical performance monitors (OPM) of technical grade, and its function class is similar to traditional spectrometer, but also will satisfy strict industrial requirements.They must relatively cheap, the compact conformation of price; And obtain almost the same power and wavelength accuracy with laboratory-scale OSAs; And need not carry out extra calibration in the length of life of this device; And can be with very high wavelength resolution and bigger dynamic range, the light of the Frequency point of monitoring close interval.

Have one can an optical band of monitor optical communication line in the OPM of all channels be very favorable.Equally, the additional function of OSNR (OSNR) with each channel of monitoring also is very useful, in order to judge the light level of making an uproar; It not only need monitor individual channel; But also want the light between the monitoring channel, therefore, further improved requirement to the spectral resolution of OPM.WDM network of today can be used nearly 200 channels in being approximately the optical communication bandwidth of 5000GHz, channel spacing is 25GHz, and these networks have benefited from OPM, and can to monitor at least 200, channel spacing be the frequency channels of 25GHz.Through ONSR is provided monitoring function, this OPM is applicable to that also monitoring and controlling channels is spaced apart in the communication system of 200GHz, 100GHz and 50GHz.

A plurality of in order to obtain simultaneously by the spectral information of monitoring frequency; Through making input light spatial dispersion and utilizing a plurality of photodetectors; Photodiode array (PDA) for example, one type technical grade OPMs has obtained all monitored parallel spectrum frequencies of spectrum of input signal and can select for use body grating (Bulk Grating), directed Fiber Bragg Grating FBG (blazed fiberBragg grating), waveguide echelle (waveguide echelle grating) or array waveguide grating (AWG) to make chromatic dispersion element (dispersive element).

The disadvantage of this method is, in photodiode array (PDA), the size of dispersion element and the quantity of photodiode all are to confirm in proportion with wavelength resolution, and therefore, this can cause, and device size becomes big, cost increases and reliability reduces.If the OSNR of each channel is measured, so a plurality of photodetectors must be set in the scattered light of individual channel.Like this, the light watch-dog of one 4 channel needs at least 12 photodiodes usually.Comprise 128 photodiodes owing to present photodiode array is general maximum, this just allows monitoring only above 30 channels.

Illustrate the United States Patent(USP) No. 5,617,234 to people such as Koga of authorizing on April 1st, 1997, disclose the synchronous monitoring circuit of multi-wavelength that accurately to discern the WDM signal wavelength and be applicable to the integrated circuit of light.The Koga recommended device is a kind of AWG (array waveguide grating), and it comprises an input port and a plurality of output port, and the output port of AWG coupling light electric explorer all.The function of AWG is: resolve into a plurality of output wave bands to input signal, the bandwidth of each wave band is b, is positioned at a class frequency f _nThe center, the output frequency that this class frequency is spaced apart Δ f>=b separates; And spatially scatter to different positions to these output wave bands, sense after export by the output port corresponding with it by output waveguide.The Koga recommended device does not possess the OSNR measurement function; Because frequency resolution is superior to the interval of interchannel; It require AWG output port quantity and monitoring channel quantity as many, and the quantity of expensive photodetector also wants consistent with the channel quantity that is detected.

AWGs is used as when look is penetrated element (dispersive element) and has brought some benefits, for example: the structure relative compact; Because it is integrated that other optical element of optical circuit can be selected on the sheet, therefore make optical loss obviously reduce and reduce the complexity of cost and optical circuit; Production technology is suitable for a large amount of manufacturings.Yet general delivery channel to limited quantity of this device provides limited frequency resolution,, normally between 8 to 40, and the frequency interval scope between the delivery channel is 400 to 50GHz.For precision monitoring OSNR, must frequency interval be reduced to far below 25GHz, because the cost of each monitor channel increases, this just needs more greatly, more expensive device.

The OPM of another kind of known type comprises and obtains the spectroscopic data point successively; And with the tunable optic filter is the basis; The output port of this tunable optic filter and a typical single-photodetector coupling; Wherein just can measure spectrum through the filter passband in the scanning main frequency scope, and in time obtain adjacent spectrum point successively.In this scheme, the tunable optic filter that is adopted should be the basis with high surface area (bulk-surface) or Volume Grating (volume-grating), directed Fiber Bragg Grating FBG, tunable linearity or toroidal cavity resonator (a tunable linear or ring resonator).Yet, use tunable optic filter also to need complicated dynamic control loop also to monitor tuning in real time, to guarantee the repeatability of spectrum.The upper wavelength resolution requirement has bigger tunable optic filter, and requires strict more at aspects such as the complexity of filter fine tuning, control loop and sensitization repeatability.

Recently; Through order and the parallel detecting method that combines the front to tell about; People have carried out some trials provides the scheme that solves ratio problems; This method with the complexity of the size of watch-dog, design for example is: the quantity of photosensitive element, and the control complexity of monitor is definite by almost (sub-linaerly) ratio according to the quantity of being kept watch on wavelength of being kept watch in the wave-length coverage.

People's such as Svilans United States Patent (USP) 6; 915; 030 transferred JDS Uniphase company, he is the assignee of this application, this patent discloses a kind of OPM based on AWG, the single output port AWG and the FSR that will have the tunable optic filter of bandwidth combine; Channel, this quantity through the monitoring greater number eliminated foregoing problems greater than the quantity of AWG output port and the photodiode that is associated.Tunable optic filter is selected the periodic subchannel through the input port input of AWG in advance; And different subchannels is sent into the input port of AWG successively, thereby the timesharing that realizes AWG and the relevant photodiode that is coupled to its output port is with the information of the channel that obtains to be determined by spectrum than the AWG output port with much bigger the manying of the quantity of the photodiode of their couplings.Although pass through to reduce the photodiode quantity of each bar AWG channel by these devices of people such as Svilans introduction; Embodied certain advantage; But in order to ensure the repeatability of light wave modulation, the tunable optic filter that it adopts must be to possess real-time monitoring and control and control circuit relative complex.

People's such as Berolo United States Patent (USP) 6,753,958 has been introduced a kind of alternative method, monitors the many wavelength of quantity with the few relatively photodiode of quantity, and does not select for use those to need the dynamic tuning frequency selective element of complicated monitoring in real time and control.The OPM that people such as Berolo propose has a light input end mouth; Through change over switch said input port and a plurality of input waveguide are coupled; These waveguides are switched by order, through some input waveguides wherein, receive the light from input port; It is offered waveguide echelle (waveguide echelle grating), and the waveguide echelle arrives a plurality of photodetectors to light scattering.Because echelle comes from the light of input waveguide according to the position scattering of input waveguide, so the light that is detected by photodetector has different centre wavelength, these centre wavelengths depend on get into echelle only through which input waveguide.When light switches between adjacent input waveguide,,, make and drift about by the centre wavelength of photodiode sampling by means of the channel spacing coefficient of WDM signal through arranging input waveguide; Can use a WDM signal sampling that the frequency period that equates with the channel spacing mark is entrained to light.

People's such as Berolo method can be monitored the WDM signal of a large amount of wavelength in the relatively inexpensive again device of compact conformation, described number of wavelengths equals the quantity that input port quantity multiply by photodiode.Yet, in people's such as Berolo method, the adjacent centre wavelength of spectrum to be sampled through coupling light in the adjacent input waveguide, wherein said adjacent centre wavelength is with the smaller portions skew of the channel spacing that equates with OPM resolution.Yet; People's such as Berolo ad hoc approach receives serious limit at least in some applications; Because when desired spectral resolution is very little; This just needs the position of input waveguide closer to each other, and such when being used for OSNR and measuring, perhaps this can cause occurring between the adjacent input waveguide unwanted optical coupling.

An object of the present invention is to provide a kind of optical performance monitor; This monitor comprises dispersion element; Wherein said dispersion element has a plurality of output ports and switchable a plurality of input port; Described input port input is used for the OSNR of the single WDM channel of accurate measurement multi-channel optical signal, and between input port, does not have unwanted optical coupling.

Another object of the present invention has provided a kind ofly carries out the method that accurate OSNR synchronously measures to a plurality of optical channels of wdm optical signal in the optical property watch-dog; Wherein through between the input port of multiple-input and multiple-output AWG, switching, the spectrum of the WDM signal of a plurality of sample frequencys is sampled.

Another object of the present invention has provided a kind of optical property watch-dog and has carried out the method that accurate OSNR synchronously measures with the many optical channels that use this watch-dog to wdm optical signal; Wherein through between the input port of multiple-input and multiple-output AWG, switching; To the spectrum of the WDM signal of a plurality of sample frequencys sample frequency of sampling; And, obtain the spectrum samples of neighbouring sample frequency range through the switching between the non-adjacent input port.

Summary of the invention

According to the present invention, a kind of optical performance monitor has been proposed, be used to monitor the OSNR of the input optical signal that comprises many WDM channels, the centre frequency of these WDM channels is with the channel frequency separation Δ _ChAverage mark separates.Said optical performance monitors comprises: dispersion element is made up of M input port and J output port, wherein M＞2 and J＞2; Control device is used for receiving input optical signal described input signal is coupled light to successively each input port input of M input port; Photoelectric detection system couples light to J output port with described photoelectric detection system, when input signal is coupled in M the input port any one port, so that the pairing signal of telecommunication of luminous power with each port of J output port is provided; And processing unit, according to the signal of telecommunication that photoelectric detection system provides, measure the OSNR of input optical signal.

According to input port and output port position separately; Dispersion element is coupled each input port input with different centre frequencies with each output port; When input light is coupled to M input port successively, can on a plurality of centre frequency sections, sample to the spectrum of input optical signal.

Be provided with J output port on the dispersion element and be used for the input port of first group of J centre frequency with the M that a couples light to input port, described first group of J centre frequency is by the frequency interval Δ _ChEvenly separate, and through predefined channel spacing Δ _ChMark departs from channel frequency, and with the light of the sensing WDM interchannel level of making an uproar, the input port of M is set to will be optically coupled to an output port in the J output port with second group of M centre frequency simultaneously, wherein said second group of M centre frequency quilt at least 2 Δs _Ch/ M separates.

The characteristic of dispersion element is to change the space look according to input port to penetrate characteristic; Wherein a plurality of centre frequencies comprise a sequence of M continuous centre frequency at least; The frequency interval of adjacent center frequencies is with many and predefined quantitative changeization, and this is owing to the spatial dispersion characteristic of input port according to dispersion element causes.

According to an aspect of the present invention, be provided with M input port, be spaced apart Δ so that the 2nd M centre frequency can be mapped to _ChOn the periodic sequence of the M an of/M sample frequency, by means of the channel frequency separation Δ _ChPerhaps its harmonic wave makes one or more the 2nd M centre frequency migrations, and wherein the frequency range of the 2nd M sample frequency covering is much smaller than two channel frequency separation Δs _Ch

On the other hand, the invention provides a kind of method that is used to monitor the OSNR of input optical signal, step is following:

A) dispersion element that comprises M input port and J output port is provided, wherein: M＞2 and J＞2;

B) J output port is set, is used for to couple light to a selected input port of M input port with first group of J centre frequency; Described first group of J centre frequency is by the frequency interval Δ _ChEvenly separate and with frequency displacement Δ f ₂Equal Δ in fact _Ch/ 2 move out of channel frequency,

C) M input port is set; Be used for so that J * (M-1) individual different centre frequency will couple light to J output port; So that when work, an output port in J the output port is optically coupled to each input port of M input port with the second group switching centre frequency; The described second group switching centre frequency is by at least 2 Δs _Ch/ M is spaced apart,

D) input optical signal is coupled to the said input port that is chosen of M input port of dispersion element;

E) utilize photodetector, detect the luminous power of each output port of J output port, to obtain J power reading and it is saved in memory;

F) successively input optical signal is coupled to each input port of other M input port of dispersion element, at every turn repeated execution of steps (e) all;

G) handle with the resulting luminous power reading of input optical signal, described input optical signal is coupled to selected in a M input port input port, with one of at least optical noise numerical value in definite WDM channel;

H) handle the power reading of storing with input optical signal, said input optical signal is coupled into remaining input port in M the input port, with one of at least optical noise numerical value in definite WDM channel;

I) utilize (g) and (h) light signal separately and the noise data that obtain in the step, the OSNR value of one of calculating in the WDM channel at least.

Description of drawings

With reference to the accompanying drawing that provides in the preferred embodiment, will the present invention be described in further detail, wherein:

Fig. 1 is the total figure that is used to monitor the optical performance monitor of input optical signal according to the present invention.

Fig. 2 a is the sample frequency figure with prior art OPM of a plurality of input ports.

Fig. 2 b is the sample frequency figure of the OPM in one embodiment of the present of invention.

Fig. 3 is the band diagram that device of the present invention is monitored.

Fig. 4 is used to monitor the OPM figure of the OSNR of WDM signal based on AWG.

Fig. 5 is the figure of the scattering properties of explanation AWG shown in Figure 4.

Fig. 6 a, 6b are central authorities and the figure of edge part of the sampling grid of explanation OPM shown in Figure 4.

Fig. 7 is the figure that the OSNR of explanation WDM signal measures.

Fig. 8 a, 8b, 8c are the partial graphs of WDM spectrum, description be the make an uproar sensitivity of measuring and the relation between the sample frequency of light.

Fig. 9 is the control circuit sketch map of OPM of the present invention.

Figure 10 a, 10b are the figure of the spectra part of WDM signal, description be the sample frequency grid that provides by OPM of the present invention.

Specify

U.S. Patent application 2005/0031259 with the application of people such as Shen name; Be incorporated among the present invention through reference at this, this application is assigned to JDSU---the application's assignee, also is the application's first inventor simultaneously; It discloses a kind of OPM in its preferred embodiment; Use multiple-input and multiple-output array waveguide grating (AWG), and the device that also proposes with Berolo of function some is similar, but have different input-output configurations.In other words; Disclosed multiple-input and multiple-output array waveguide grating (AWG) adopts the configuration of fine setting (Vernier) input port in the application 2005/0031259; Make when input signal when an input port is switched to next input port; Through relatively big frequency change sample frequency is changed, for example frequency change equals the WDM channel spacing and adds/subtract a smaller mark, and this mark limits the total spectral resolution of OPM.Therefore; The incoming wave conduit of M the Vernier input port of disclosed formation OPM is placed enough far each other in application 2005/0031259; Be unlikely to cause the appearance of unwanted waveguide coupling phenomenon like this, the waveguide coupling can damage the performance of Berolo OPM.

The present invention has further improved U.S. Patent application 2005/0031259 disclosed OPM; And an OPM improvement, that have a plurality of switchable input ports has been proposed, wherein a plurality of switchable input ports are used for monitoring with the OSNR of higher certainty of measurement to the individual channel of multichannel WDM signal.

Fig. 1 has demonstrated and has used multiple-input and multiple-output AWG to monitor the embodiment of the Optical devices of light signal.

In order to monitor the input optical signal that is in the individual different optical frequencies of K (K＞1), device 1 has been equipped with dispersion element 101, and it is placed between 1 * M conversion equipment 330 and the photodetector device 181, hereinafter installs 1 and will be called as OPM1.1 * M conversion equipment 330 also simply is called switch 330 hereinafter.In other embodiments; Available N * M switch substitutes 1 * M switch 330; Reach N the shared said OPM1 of input optical signal like this; They are propagated in waveguide (for example optical fiber) separately, monitor the optical spectrum and the OSNR of each signal successively, as the application's hereinafter introduced to single WDM input.The dispersion element 101 that occurs with array waveguide grating (AWG) form comprises M input port 100 ₁To 100 _MAnd J output port 110 ₁To 110 _J, hereinafter generally is called input port 100 and output port 110 respectively.Switch 330 has controlled function, between input port 100 any input ports of the input port 30 of OPM1 and AWG 101, optical coupled is provided, as among the figure with shown in the arrow 310.When input signal was coupled into each port of M input port, output port 110 optical coupled of AWG 101 were to photodetector device 181, and photodetector device 181 is to comprise J photodiode 180 ₁To 180 _JThe form of photodiode array (PDA) assembly occur; One of different output port 110 of each photodiode and AWG 101 carries out optics and connects; Detecting light output and to provide in each port with J output port the corresponding signal of telecommunication of luminous power to import, the above-mentioned signal of telecommunication is the luminous power reading mentioned of hereinafter just.

Notice that in other embodiments AWG 101 possibly replaced by other dispersion element, for example: waveguide, echelle (echelle grating) or body grating or the like, the those of skill in the art in present technique field are appreciated that.Dispersion element 101 among the embodiment is preferably accomplished on the PLC chip with switch 330.Photodetector device 181 can have other optional implementation method, for example realizes with electric charge coupling array device.

Device 1 has also had control and processing unit electric, does not show among these Fig. 1, comprises the controller that is used for control switch 330 at least; Be used to collect and store the memory of the information that detects by photodetector device 181; And be used to handle collected information processing device, for instance, be used to measure OSNR from the input optical signal of the signal of telecommunication; The said signal of telecommunication is provided by said photodetector device 181, and is used to export treated information.Switch 330 and corresponding controller thereof comprise control device, are used for input optical signal is coupled into successively M the input port 100 of AWG 101 ₁To 100 _MEach port.

In AWG 101; According to input port and output port position separately; Width with different centre frequencies being the center is in the b narrow band; Each input port of input port 100 carries out optics with any output port of output port 110 and is connected, and illustrates m input port 100 _mOnly in narrow frequency band, export 110 with j _jPort carries out optics and connects, and said narrow frequency band is by with different centre frequency f _{M, j}For the width at center is the transmission function T of b _{M, and j (f-fm, j)}Definition, hereinafter, centre frequency f _{M, j}To be called as sample frequency; M input 100 _mAlso can be with another center frequency point f _{M, j+1}=f _{M, j}+ Δ f ₁Be connected with adjacent (j+1) individual output port, wherein frequency interval Δ f ₁Bigger than bin width b in fact, preferably multiply by coefficient M.

With regard to function, the input signal that dispersion element 101 will be coupled into any input port 100 carries out scattering according to its spectrum, and J spectrum with input signal in frequency band range separately is coupled into J different output port 110 ₁To 110 _J, according to input input port and output port position separately, with m input port 100 _mIn J the related spectrum each is with J spectral centroid transmission frequency f _{M, j}=1 ..., different one among the J is spaced apart Δ f for the center common formation of J above-mentioned spectral centroid frequency ₁The m group { f} of centre frequency _m={ f _{M, j=1}, f _{M, j=2}..., f _{M, j=J}And across frequency range be F _J=(J-1) Δ f ₁, will be called as the operating frequency range of AWG 101 hereinafter.Attention: arbitrary port of input port 100 is preferably selected duplicate first frequency interval delta f ₁, just m can be the arbitrary value between 1 to M, but that kind of introducing just as hereinafter, if input port 100 is arranged to such an extent that relatively disperse, frequency interval just can be adjusted according to input port m.Next we at first consider a kind of situation, as Δ f ₁When being counted as independently during input port, just, when the quantity of input port is enough little, make Δ f between the input port 100 ₁Variation accumulate and do not exceed frequency range F _J, this frequency range F _JExceeded the preset sampling frequency tolerance.

When input light was coupled into M input port successively, in order to gather input optical signal with a plurality of centre frequencies, the dispersion element 101 that will have output port 110 cooperated use together with PDA181.These a plurality of centre frequency f _{M, j}, wherein, m and j are integer, 1≤m≤M and 1≤j≤J is by M J row centre frequency { f} _m, m=1 ..., M forms, and hereinafter also will be known as a plurality of centre frequency { f _{M, j}.Said a plurality of centre frequency { f _{M, j}Comprise a K different optical frequency, preferably consistent with it.

Attention: AWG 101 is different from traditional demultiplexing (de-multiplexing) AWG that has a plurality of input ports and a plurality of output ports, as people's such as Koga United States Patent (USP) 5,617,234 exemplified describe the same, explained the synchronous monitoring circuit of multi-wavelength.In fact, the function that has a demultiplexing AWG of a plurality of input ports comprises: the light signal that will be coupled to any input port resolves into the wavestrip of approximate periodic intervals; And scattering to different positions to them, their can be detected by the output wave conduit there, respectively by each self-corresponding output port output.In the structure that Koga introduced, for input port and output port, adopt foregoing symbolic notation, when position of incoming wave conduit change in location, center transmission frequency f _{M, j}And also channel of cyclic variation of the communication between the output port, mean f _{M, j}=f _{M+1, j+1}That is to say, if AWG 101 is as Koga is described, if input optical signal is with centre frequency f _{M, j}Propagate in the channel for the center, if input light is coupled to m input port 100 _m, signal will be from j output port 110 _jOutput, and if input light is coupled to (m+1) individual input port 100 _(m+1), signal will be from (j+1) individual output port 110 _(j+1)Output.The function of tradition AWG allows to use arbitrary input port, is used for frequency demultiplexing (de-multiplexing) signal, and this signal has the optical channel of periodic intervals aspect frequency.

That AWG had was functional opposite with the demultiplexing (de-multiplexing) of the prior art that has a plurality of input ports, the input port 100 of AWG ₁To 100 _MBe used as dispersion element 101 of the present invention, so:

f _m，j≠f _m+1，j+1， (1)

For some right input of port at least separately, just, at least a portion, and preferred input port 100 and output port 110 is whole, index j=1 ..., J-1, m=1 ..., M-1.In more detail, make up M input port 100, make input couple light to a port in J the output port 110, illustrate, be coupled to j output port 110 _j, with one group of M centre frequency { f} _J={ f _{M=1, j}, f _{M=2, j}..., f _{M=M, j}, be known as the second frequency of M centre frequency hereinafter.In this group, every two adjacent centre frequency f _{M, j}, f for instance _{M ', j}And f _{M '+1, j}, by second frequency interval delta F ₂(m) separate, said second frequency is different from first frequency interval delta f at interval ₁Or its any harmonic wave, just:

(f _m，j-f _m+1，j)＝Δf ₂(m)≠Δf ₁. (2)

Second frequency interval delta f ₂, be sample frequency f _{M, j}And f _{M+1, j}Between frequency drift, it can rely on input, said sample frequency f _{M, j}And f _{M+1, j}Be associated with adjacent 2 ports of M input port 100 and the same port of J output port 110; Shown as the RHS middle port call number m of equality (2); Just; Different input/output ports that can be adjacent with input port 100 are to differentiating, and this also representes one group of J sample frequency { f} _m={ f _{M, j=1, J}Relative drift between certain two, said one group of J sample frequency is associated with adjacent 2 ports of M input port 100, and input port 100 for instance _mWith 100 _M+1Attention: when input optical signal is coupled to output port 110 ₁To 110 _JAmong a port time, said second frequency interval delta f ₂(m) also be at input port 100 ₁To 100 _MThe frequency interval of the centre frequency of the spectrum of received input optical signal, input.Therefore relational equation (2) means: with regard to the frequency interval between center transmission frequency, AWG 101 is asymmetric, and above-mentioned frequency interval depends on the port one 00 as one group of input port _1...MOr 110 _1...J

Input port 100 is by preferred disposition, so that make said second frequency interval delta f ₂(m) equal frequency factor δ f=Δ f ₁The integral multiple of/M, just:

Δf ₂(m)＝k _m·Δf ₁/M， (3)

Integer k wherein _mPreferably satisfy:

k _m≥2， (3a)

And one group of M frequency { f} _mBe not always the case, this group interpolation is also constituted sample frequency f together _{M, j}The cycle grid, said sample frequency f _{M, j}Have and be about δ f=Δ f ₁The cycle of/M.One class frequency { f} _jThe frequency range that covers:

$F_M=\frac{\mathrm{\Δ}{f}_1}{M}\underset{m=1}{\overset{M-1}{\mathrm{\Σ}}}{k}_m,---\left(4\right)$

This is known as fine setting (Vernier) scope of AWG 101 hereinafter.Frequency factor δ f has determined the frequency resolution of apparatus of the present invention 1.

In one embodiment, just, as US patent application 2005/0031259 introduced, have 4 input ports 100 at least, M＞3 just so make up, and make M centre frequency { f} _jBe evenly to separate n _m=n=M ± 1, and

Δf ₂＝Δf ₁·(1±1/M)， (5)

Attention: conditional equality (3a) makes a distinction OPM 1 with the spectrometer that people such as Berolo propose, in that spectrometer, the symbolically method so defines, Δ f ₂=Δ f ₁/ M, corresponding to a wideer interval, and favourable part is that in the present embodiment, littler unnecessary light is coupled mutually between input port 100, wherein input port 100 comprises optical waveguides.

In operating process, input optical signal is coupled to input port 30, and input port 30 has 1 * M optical switch 330, is used to monitor above-mentioned signal.The major function of 1 * M optical switch is to set up light path, and each port of said light path input optical port 100 of 101 from input port 30 to dispersion element is from port one 10 ₁To 110 _M, shown in arrow 310, the light path of expression input signal is created according to each input port that time sequencing switches to dispersion element 101 successively by optical switch 330.

For instance, input comprises from a plurality of { f _{M, j}The light input signal of all frequencies at first be coupled into input port 100 ₁, and the information of relevant light input signal input, the luminous power in the corresponding passband range of dispersion element 101 for example, this transmission band is with one group of J sample frequency { f} _M=1Be the frequency center:

f _1，j＝f _1，1+(j-1)·Δf ₁，j＝1，...，J (6)

These information are by J photodetector 180 ₁To 180 _JGather.

Next, input signal is coupled into second input port 100 of dispersion element 101 ₂, do not show among Fig. 1 that the information of relevant input light is by J photodetector 180 ₁To 180 _JWith one group of J sample frequency f ₂, j=1 ..., J, { f} _m=2 gather sample frequency, a said J sample frequency and second input port 100 ₂Be associated.

Consider an embodiment at this, wherein made up M input port 100, therefore satisfy equality (5), Δ f ₂=Δ f ₁(1+1/M), and as far as input port 100, first frequency interval delta f ₁Change very little, sample frequency f _{2, j}Satisfy equality:

f _2，j＝f _1，1+(j-2)·Δf ₁-δf (7)

Go on foot switched input signal continuously with M, through M input port of dispersion element 101, and each step all use J frequency frequency subsets separately, gathering also, storage signal obtains the information { f} of the M sub-set of J sample frequency for information about _m, m=1 ..., M.

f _m，j＝f _1，1+(j-m)·Δf ₁-(m-1)·δf. j＝1，...，J，(8)

Use 2 different cycle Δ f ₁With Δ f ₂, cycle Δ f ₁The segmentation cycle Δ f that the factor generates ₁The vernier of/M, this and famous Vernier vernier are similarly, for example the Vernier vernier caliper; Therefore, the M of dispersion element 101 input port is known as the Vernier input port hereinafter.The number range that is shown among Fig. 2 a is J=8, the embodiment of M=3, and δ f=Δ f ₂-Δ f ₁=Δ f ₁/ M=Δ f ₁/ 3.Each vertical vertical bar symbolically representes to satisfy the sample frequency f of equality (8) among the figure _{M, j}In a frequency.What uppermost row 311 was described is and first input port 100 ₁One group of relevant sample frequency { f} _m=1, comprising: sample frequency f _1,111, f _1,212 ..., f _1,818; Second row 312 is described be with second input port 100 ₂One group of relevant sample frequency { f} _m=2, second input port 100 ₂In Fig. 1, do not show; What last column 313 was described is and last input port 100 _M=3One group of relevant sample frequency { f} _m=3, comprising: sample frequency f _3,131, f _3,232, f _3,333 ..., f _3,838.

Attention: the sample frequency collection { f} that is associated with adjacent input port 100 _mIn per two frequencies, for instance, between 311 and 312,312 and 313, change second frequency interval delta f each other ₂, so just crossed first frequency interval delta f ₁

In order to make comparisons, Fig. 2 b has shown by people such as Berolo at United States Patent (USP) 6,753; The sample frequency of disclosed prior art spectrometer is arranged in 958; Wherein, comprise a plurality of light input end mouths that link to each other with dispersion element, switchable, said dispersion element is with the appearance of echelle filter.Attention: in the device that Berolo proposes, the pairing sample frequency sequence 301,302 of adjacent input port and 302,303 differs period 1 Δ f each other ₁Factor delta f=Δ f ₁/ 3, the sampling grid { f that makes in generation _{M, j}, m=1, on 2,3, adjacent sample frequency is associated with adjacent input port.Disadvantage is: find such arrangement, can cause at least when dispersion element 101 be AWG and input port 100 when being waveguide, undesirable optical coupled appears between adjacent input port 100.

Get back to Fig. 2 a, shown is embodiments of the invention, arranges the input port 100 of dispersion element 101 ₁To 100 _M,, Δ f is arranged for all input ports 100 ₂-Δ f ₁=Δ f ₁/ M, and the quantity J of output port 110 surpasses all sample frequency { f of quantity M of input port 100 _{M, j}, comprise evenly spaced sample frequency f _{M, j}, said sample frequency f _{M, j}Frequency interval between frequency f _1,1And f _{1, J '}Between, wherein: J '=(J-M+1), this has constituted one is the sample frequency cycle collection at interval with δ f, comprises M frequency of K=(J-M) at least, promptly aforementioned first group of K different light frequency.Utilize the OPM 1 of present embodiment, through at output port 110 measuring light power, when input optical signal switches successively, at frequency range (F between M Vernier input port 100 _J-F _M) in, the spectrum of input signal can be by uniform sampling, just in frequency f _1,1And f _{1, J '}Between, spectral resolution is δ f=Δ f ₁/ M, it is the multiple of M, and is littler than the single input resolution that AWG provided of the tradition of other similar design.

Borrowing this example, the for example clear input optical signal spectrum that uses device of the present invention to obtain to have monochromatic light spectral line 400 of Fig. 3.In this example, dispersion element is AWG, and parameter is: M=8, Δ f ₁=100GHz, Δ f ₂=87.5GHz, δ f=12.5GHz, J=40 uses present available manufacturing technology can it be created.Be coupled into 8 output ports 100 of dispersion element 101 successively when input light ₁To 100 _M=8The time, that 8 lines of SV1 to SV8 mark show is transmission wave band: 401-404,411-414 ... 471-474, adjacent 4 output ports of the output port J=40 of corresponding chromatic dispersion element 101.Transmission wave bands 401,402 shown in Fig. 3 etc. are represented by bell-shaped curve, description be spectral transmissions function T separately _{M, j}(f-f _{M, j}), each spectral transmissions function is with sample frequency f _{M, j}In different frequencies be the center.Transfer function T _{M, j}(f-f _{M, j}) also be known as sampling function; Can be measured, for example through the light wave of coupling, like light wave from tunable laser from the tunable wave length monochromatic source; It is coupled into m the input port of AWG 101, and measures the luminous power of j output port according to laser light wave frequency f.Attention: transmission wave band 401 is corresponding with different output ports with 411, and transmits wave band 411 and 402 corresponding to the same port in the output port 110, and corresponding to 2 the adjacent ports in the input port 100.

Design AWG 101: between the transmission wave band, the overlapping of appropriateness arranged, illustrate, 401 and 411, they are adjacent on the frequency domain space, their centre frequency differs δ f=12.5GHz, and is as shown in Figure 3; But the transmission wave band adjacent with the next one has only very little wave band overlapping, and the transmission wave band that the said next one is adjacent separates with 25GHz in the transmission spectrum 415 of AWG.In order to calibrate, overlay information is preferably kept in photoelectric storage (not showing among the figure) lining of device 1.In some embodiments, preferred option: on the spectral transmissions wave band, adjacent wave band is more severely, as shown in Figure 3 overlapping, for instance, and function T _{M, j}(f-f _{M, j}) waveband width b be 3dB, near frequency sampling step-length δ f, between b～δ f, spectrum does not need the slit just to be obtained.Favourable part is: the layout of Vernier input port of the present invention; Wherein, At an adjacent group switching centre frequency collection spectrum; For instance, through between non-adjacent input port, switching the collection of accomplishing 411 and 402 spectrum, can avoid occurring each other undesirable optical coupled.

In each consecutive steps, at each transmission wave band T (f-f _{M, j}) on; The part of spectrum line 400 is detected by the photodetector that is derived from photodetector array assembly 181 180; Said photodetector array assembly 181 is connected with the corresponding output end mouth of dispersion element 101, and the luminous intensity reading value 40 that is provided by photodetector is saved in the memory.After importing input signal in proper order through all 8 input ports; All stored datas can be used to generate digitized spectrum line 410; Input is reproduced input spectrum line 400 with the digitization frequencies scale of frequency step δ f=12.5GHz; As the simple and clear transmission spectrum through dispersion element 101 415 was described, SV1-SV8 obtained spectrum 415 through stack AWG transmission spectrum, and affiliated transmission spectrum SV1-SV8 is corresponding to being coupled to 8 input ports 100 successively ₁... 100 _M=8The input signal of each port.Alternatively, if an optical channel of spectral line 400 expression WDM signals, so in a channel grid periodic regime of relevant said optical channel, only corresponding to centre frequency or sample frequency f _MjThe luminous power reading can be used to determine said channel 400.

Monitoring WDM (wavelength division multiplexing) signal

Embodiment at this various details optical performance monitor (OPM) 1; Be arranged to and monitor the multichannel optics WDM signal S that comprises many WDM channels;, comprise the synchronization monitoring of the OSNR of each WDM channel, and will explain hereinafter according to this method for supervising of the present invention.

Multi-channel optical signal S has the WDM channel, and said WDM channel is provided with by equifrequent ground, just, for arbitrary integer channel index n, has with the channel frequency separation Δ _ChThe central channel frequency ν that evenly separates _n, frequency interval, just (ν _N+1-ν _n)=Δ _ChFor example, channel frequency ν _nBe set on the ITU grid, and be the multiple of 100GHz, use Δ _Ch=100GHz.In another example, they can be the multiple of 50GHz, use Δ _Ch=50GHz.Frequency scaling (frequency scale) by equality (9) definition after this will be called as channel frequency grid { ν _n}:

ν _n＝ν ₀+n·Δ _ch，n＝0，1，...，(9)

ν wherein ₀Be predetermined minimum channel frequency.In typical application, OPM 1 can be arranged to the 40WDM channel of monitoring simultaneously on 100GHz ITU grid, or the 80WDM channel on 50GHz ITU grid, and this is the typical amounts of channel in the C-band optical communication system.

For accurate monitoring, advantageously WDM signal S to be sampled with sample frequency, said sample frequency is to equal the channel separation Δ _ChThe cycle of the integer part of/M ' forms period grid, and wherein M ' is the sampled point quantity of each channel frequency separation, so that each channel grid cycle (ν _n-Δ _Ch/ 2, ν _n-Δ _Ch/ 2) with respect to channel frequency ν separately _nIdentical precalculated position comprise the individual frequency sampling point of M '.By the period frequency grid of a plurality of definition in all these nominal values, perhaps with the channel separation Δ _ChAfter this integer part of/M ' target frequency sampling location at interval will be called as target frequency sampling grid and be represented as ∑ _{M '}

Target sampling grid can be by approximate, for example has the embodiment of OPM1 of the quantity M=M ' of input port 100 through use, and the quantity J of output port 110 equals the sum of monitored WDM channel at least, and with first frequency interval delta f ₁=Δ _ChDispose said output port 110.Yet, by a plurality of centre frequency { f of this device _{M, j}The sampling grid that the provides sampling grid ∑ that will depart from objectives inevitably _{M '}=∑ _M, and possibly cause the loss of spectrum and OSNR monitoring accuracy.In an embodiment of the present invention, center sampling frequency f _{M, j}With target sampling grid ∑ _MDeviation, and the unfavorable effect of this deviation in the OSNR monitoring is suitably reduced.

At first, will describe the actual cause that can produce sample frequency grid heterogeneous with reference to figure 4, said sample frequency grid uses all centre frequency { f of dispersion element 101 _{M, j}In a plurality of formation, Fig. 4 illustrates the embodiment of OPM1 of the present invention, it is arranged in wide frequency ranges the OSNR of monitoring multichannel WDM signal S.

In this drawing; Among the embodiment therein; Dispersion element 101 is clearly illustrated as AWG 101, and said AWG 101 comprises the array of length increment waveguide 130, and it carries out optics with input concave surface slab (concave-slab) waveguide 140 with output concave surface slab waveguide 150 and is connected.The waveguide 140 of input concave surface slab is connected to each in the length increment waveguide 130 with each optics in M the input waveguide port one 00, and export concave surface slab waveguide 150 each optics in the length increment waveguide 130 is connected to each in J the input and output waveguide port 110.

Said J output waveguide port one 10 is connected to output concave surface slab waveguide 150 along focal curve 160 by optics at their first ends 111, and it has limited the slab waveguide 150 with respect to the output of waveguide array 130.Said M output waveguide port one 10 is connected to the photodetector array 181 with J photodetector 180 at their second ends 112.

Multichannel input optical signal S with spectrum S (f) is sent to 1 * M optical switch 330 through the optical fiber 20 of the input waveguide port 30 that is connected to OPM1, can be in regular turn input optical signal be coupled in each in M the input port 100 of AWG 101.In case said input optical signal is coupled into a port; M port of input port 100 for example; Then waveguide array 130 according to spectrum S (f) with said light signal from m port of input port 100 to J output waveguide port one 10 chromatic dispersions; So that receive the spectra part of importing light along each position x of focal curve 160, the spectra part of said input light is with different center frequency f=f _m(x) be the center.Function f=f _m(x), wherein x is the space coordinates along focal curve 160, is described in the spatial dispersion of first end, the 111 light frequency f of place of the reception of output waveguide 110, and said output waveguide 110 is used to couple light into m port of input port 100.As explanation, curve 441 and 442 schematically shows the chromatic dispersion function f of AWG 101 of two adjacent input port m and the m+1 of M input port 100 among Fig. 5 _m(x) and f _M+1(x), 1≤m≤M-1.Curve 441 with 442 separate and their slope depends at m of input concave surface slab waveguide 140 relative position with m+1 input waveguide; Therefore input waveguide 100 each other the closer to; Then dispersion curve 441 and 442 each other just the closer to, thereby frequency drift Δ f ₂Just more little.

According to their position along focal curve 160, output waveguide 110 is used for having J sampling function T (f-f from the portions of the spectrum of the separation of length increment waveguide 130 reception input optical signals _{M, j}) spectrum S (f) sample said sampling function T (f-f _{M, j}) with separately centre frequency or sample frequency f _{M, j=1}..., f _{M, j=J}Be the center, wherein integer m and j are of before this, refer to the input and output waveguide respectively.Photo detector array 181 offers processing unit with J power reading, and said J power readings signify is with sample frequency { f} _m={ f _{M, j=1}..., f _{M, j=J}The spectrum S (f) of input optical signal S is sampled.

S _m，j(f _m，j)～∫T(f-f _m，j)·S(f)df，j＝1，...，j， (10)

Through in regular turn the input signal S between input waveguide port one 00 being changed and deposits power reading S _{M, j}, input signal spectrum S (f) quilt is with the sample frequency grid Sampling, said sample frequency grid { f _{M, j}By M interlacing scan frequency set { f} _mForm, m=1 ..., M.Said sample frequency grid { f _{M, j}Evenly separated with relative frequency interval δ f, if following condition is satisfied: all interlacing scan frequency set { f} that a) are correlated with different input ports 100 _mWith with the irrelevant same frequency interval delta f of input port ₁Evenly separated, b) input port 100 is configured so that M " folding " sample frequency f ' _{M=1, j}Collection { f ' } _j

{f’} _j＝{f’ _m＝1，j，f’ _m＝2，j，...f’ _m＝M，j} (11)

With relative frequency interval δ f=Δ f ₁/ M is evenly separated,

Wherein, obtain and separately sample frequency f according to equation _{M, j}Be correlated with " folding " sample frequency f ' _{M, j}

f’ _m，j＝f _m，j+(f _1，j-f _m，j)mod(Δf ₁)，m＝1，...，M，(12)

Wherein, function (x) mod (y) expression ask modular arithmetic, result be x divided by y after the remainder of gained, according to equality (11) and (12), M input port 100 is configured so that second group of { f} in M centre frequency _jCan be drawn into M sample frequency f _{M, j}Periodic sequence, in other words, can be converted into M " folding " sample frequency f _{M, j}Periodic sequence, through one or more skew first frequency interval delta f with second group in M the centre frequency ₁Or harmonic wave wherein, with Δ f ₁/ M said at interval " folding " sample frequency f _{M, j}

Condition (a) and (b) require in predetermined tolerance range, for all output port 100 sample frequency f _{M, j}And f _{M+1, j}Between frequency drift Δ f ₂(m) keep identical basically.Yet; This is impossible realize; Wherein, dispersion element 101 is a characteristic with spatial dispersion characteristic D=df/dx, and this spatial dispersion characteristic depends on input port and changes; As it often is among the AWG of real life, the dispersion element of bulk wave guide grating and classification waveguide optical grating and other types.

With reference to figure 5, spatial dispersion characteristic D just along the change speed of the light frequency f of the dispersed light of focal curve 160, has defined the slope of curve 441 and 442.In the illustrated embodiment, for each input port 100, this slope is approximately constant, does not just rely on the space coordinates x that crosses waveguide end 111, so that the average headway of first waveguide 111 provides approximate evenly spaced sampling set { f} _mAlthough D depends in the position of the port one of input waveguide separately 00 of input slab waveguide interface 144, therefore depend on input waveguide port one 00 and change.Thereby line 441 and 442 has Different Slope D _m≠ D _M+1, and when m and m+1 input port removed far away the time this difference can increase.Therefore, relevantly with the m input port satisfy equation DELTA f ₁(m)=D _mThe frequency interval 471 of the sample frequency of Δ x is different from the frequency interval 472 of one group J the sample frequency relevant with the m input port, Δ f ₁(m+1)=D _M+1Δ x wherein, is Δ x=(x for the output port location gap of the receiving terminal 111 of output port 110 _J+1-x _j).

As for the good AWG 101 of design, the discrepancy delta D=(D of the spatial dispersion characteristic that is associated with adjacent input port 100 _m-D _M+1) generally quite little., its effect can be gathered on a large amount of output ports, with and effect can cause frequency drift Δ f ₂(m)=(f _{M, j}-f _{M+1, j}) obvious change, as through relatively understanding corresponding to the frequency drift 477,475 of output port position 445 and 447.These change the sampling frequency deviation amount δ f that produces accumulation _Off=| f _{M, j}-f ^* _{M, j}|～F _JΔ D/D _m, f wherein ^* _{M, j}Be distance objective periodic sampling frequency grid ∑ _MThe respective frequencies position, surpass predetermined threshold, for example, relative frequency is the predetermined portions of δ f at interval.

Notice sampling frequency offset δ f _OffAnd spatial dispersion characteristic variations Δ D is proportional between the input port, and it depends on the relative position of input Vernier port one 00 successively, and for the input port far away of being separated by, this error is general bigger, thereby and with big frequency drift Δ f ₂(m) be associated.Therefore, configuration input port 100 is so that Δ f ₂(m) suitably reduce, satisfy condition simultaneously (3), (3a), (11) and (12) are favourable.

As an example, the AWG101 of OPM1 has M=8 input port and J=40 output port, and is arranged to sampling WDM signal, and said WDM signal comprises and is arranged in the Δ with sample frequency step-length δ f= _Ch40 WDM channels on the 100GHz ITU grid of/M=12.5GHz.Output port 110 is arranged to provides one group of 40 sample frequency, and for an input port, said sample frequency is with first frequency interval delta f ₁The ≌ Δ _Ch=100GHz evenly separates, for example, and m=4 port of input port 100.In maybe embodiment two of table 1 below this and 2 explanations AWG 101 of the present invention many, they construct different with their input ports 100.In every kind of situation, M=8 input port 100 is configured to provide and is illustrated in the table M sample frequency { f in the third line _{M=1, j}, f _{M=2, j}... f _{M=M, j}Second group of different { f} _j, and corresponding to one of in the output port 110, for example, the j=20 port.{ f}j satisfies equality (3), (3a), (11) and (12), integer k to second group of the sample frequency that in table 1 and 2, provides _mSuch as in equality (3) qualification.For relatively, table 3 provided and also corresponding to as the input port structure of description such as Berolo.

With reference to figure 2a and 3, table 1 is corresponding to the embodiment of the AWG 101 described in the preceding text, and wherein M Vernier input port 100 is configured so that the second class frequency { f} of M centre frequency _J={ f _{M=1, j}, f _{M=2, j}..., f _{M=M, j}With frequency drift Δ f ₂=Δ f ₁(1-1/M)=87.5GHz evenly separates, and scope is greater than 600GHz.Unfriendly, we find that the big like this frequency interval that is associated with Vernier port one 10 can cause the grid { f that samples _{M, j}Sizable irregular, at operating frequency range F _JThe edge have the sampling frequency deviation amount δ f that surpasses about 6GHz _Off, span is 4THz in this case.

Table 1

Input port call number m	1	2	3	4	5	6	7	8
									k m	0	7	7	7	7	7	7	7
f M, j-f 1, j, GHz	0	-87.5	-175	-262.5	-350	-437.5	-525	-612.5

Table 2 disposes M input port 100 so that one group of M sample frequency { f in this embodiment corresponding to embodiment _{M=1, j}, f _{M=2, j}..., f _{M=M, j}Anisotropically separate the each changes delta of said frequency frequency interval with the frequency interval between two adjacent center frequencies _Ch/ M=12.5GHz; A class frequency { f who provides in the present embodiment _{M=1, j}, f _{M=2, j}..., f _{M=M, j}Scope only be 187.5GHz, just less than 2 Δ f ₁, and have the only average frequency interval of about 26.8GHz.Advantageously, this configuration generally provides the more sample frequency grid { f of rule _{M, j}, have the sampling frequency deviation amount δ f that is equal to or less than about 3.5GHz in the edge of 4THz operating frequency range _Off

Table 2

Input port call number m	1	2	3	4	5	6	7	8
									k m	0	2	2	2	3	2	2	2
f M, j-f 1, j, GHz	0	-25	-50	-75	-112.5	-137.5	-162.5	-187.5

[104] although the class frequency { f} that the configuration of input port as shown in table 3 100 provides _jScope only be 87.5GHz; Each continuous sampling frequency distance front sample frequency about minimum frequency space of 12.5GHz only wherein; It is found in and produces undesirable optical coupling between the input waveguide 100; As stated, it uses this configuration possibly cause not satisfied OPM performance.Therefore, preferably, in OPM1 of the present invention, the M of AWG 101 input port 100 is configured so that two adjacent input ports 100 and sample frequency f _{M, j}Be associated said sample frequency f _{M, j}Not by a plurality of centre frequency { f _{M, j}Adjacent frequency in the sample frequency grid that forms.In addition preferably, second of M sample frequency group of { f _{M, j}Less than 3 Δs _ChFrequency range F _MIn, more preferably less than 2 Δs _ChIn addition preferably, frequency range F _MLess than 300GHz, more preferably less than 100GHz.

Table 3

Input port call number m	1	2	3	4	5	6	7	8
									k m	0	1	1	1	1	1	1	1
f M, j-f 1, j, GHz	0	-12.5	-25	-37.5	-50	-62.5	-75	-87.5

As an example, for the embodiment that has corresponding to the AWG 101 of the input port of table 2 100 configurations, Fig. 6 a and 6b are to its sample frequency grid { f _{M, j}Be illustrated.Black rhombus 710 expression sample frequency f _{M, j}, and vertical bar 700 expressions have the target sampling grid ∑ in 12.5GHz cycle _MThat Fig. 6 a representes is the center, that 150GHz is wide, approximate sample frequency grid { f corresponding to 15＜j＜25 _{M, j}Part, wherein sampling interval is still near the design load of 12.5GHz, and sample frequency is equally distributed basically.

Yet, more near the edge of the operating frequency range of OPM, sampling grid { f _{M, j}Become very irregular more, as having the sample frequency grid { f of j＜6 shown in Fig. 6 b _{M, j}The edge part, sample frequency f wherein _{M, j}With the same big frequency offset δ f with about 3.5GHz _Off720 depart from the target location on the 12.5GHz grid, and this has adverse effect to accuracy and the dynamic range that OSNR measures.

OSNR (OSNR) is measured

The OSNR of optical channel is defined as the total optical power P of the signal component of the optical channel signal in the channel width scope _nSpectrum power P to optical noise _NRatio, measure with dB usually:

OSNR _dB＝10·log(P _ch/P _N). (9)

The optical noise power P _NGenerally, confirm through measure spectrum power at the spectrum position place of the spectral regions that fully occupies away from signal component by the WDM channel.This explains that in Fig. 7 Fig. 7 illustrates the spectra part of WDM signal, and said WDM signal comprises with frequency ν _nAnd ν _N+1Two adjacent WDM channels for the center.The signal component of channel occupies the frequency spectrum in peak 210 and 220.Equally, show Noise Background (noise floor) 230.

Use has frequency resolution δ f=Δ _ChThe embodiment of the OPM1 of/M; M>=3 wherein; Use for example to be used for one of known signal Processing Algorithm of looking at the peak, through to peak 210 and 220 samplings and estimation at each by the peak 210 of sampling, zone below 220, can estimate in two channels the optical signal power of each.The optical noise of each channel can be to be understood that like those skilled in the art through to sampling in the both sides of each signal peak and asking on average and estimate.For example, through the spectrum of position 205 and 215 being sampled and, calculating sampling function T average to asking of two power readings (power reading) _{M, j}(f-f _{M, j}) width, can measure the noise power P of first channel 210 _N1Likewise, ask on average, can estimate the noise power P of channel 220 through the power reading that the spectrum sample to spectrum position 215 and 225 obtains _N2

The United States Patent (USP) 6 of Berolo etc.; 753; 958 have explained the measurement to the OSNR of WDM signal, and it uses the echelle based on the frequency spectrum analyser with a plurality of convertible input ports, when being coupled into first port of input port when input signal with one group and channel center frequency ν _nCorresponding to sample frequency is sampled to the WDM signal spectra, is used for confirming the channel signal power P _Ch, and with sample frequency of another central authorities of group between adjacent channel the spectrum of WDM signal is sampled when being converted into second port of input port at input signal, be used for confirming the optical noise power P _NThis method can accurately provide, and the said sample frequency group relevant with two input ports all evenly separated with the frequency of identical constant frequency interval, and said frequency interval equals the channel separation Δ on the whole operating frequency range of device _ChThough, if the operating frequency range F of the monitored device of WDM channel therein _JFor big, for example in whole S, C or L-band scope, then this can not be as the reason of describing with reference to figure 5 before this.Moreover; Input signal when an input port is received with channel center frequency sampling input WDM signal and when signal is coupled into another input port at the sampling input WDM of central authorities of WDM interchannel signal, may in the whole operating frequency range of device, be subjected to the variation of unwanted OSNR measuring accuracy and/or dynamic range.

Veritably, the accuracy that OSNR estimates can be very sensitive to frequency sampling, especially for the noise samples location, for example for sampling location 205,215 relevant with signal peak 210 and 220 among Fig. 7 and 225 accurate position.Usually, through to signal spectra with channel frequency grid ν _n=(ν ₀+ n Δ _Ch), n=0,1 ... basic first grid positions, just with frequency ν _{N ±}

=ν _n+/-Δ _Ch/ 2 sample, and can obtain Noise Estimation more accurately, so that minimize the optical signal component in the sampling noiset reading.This will further specify in Fig. 8 a-8c, as an example, the spectra part of the WDM signal that comprises 5 adjacent WDM signals 510,520,530,540 and 550 will be shown, said 5 adjacent WDM signals in not having noise with Δ _Ch=50GHz is spaced apart.Said WDM signal is to be sampled by the isolated sample frequency of δ f=12.5GHz, and is represented by black diamond symbols as in the drawings, 4 samples of each channel.In Fig. 8 a, some sample frequency is accurately corresponding to the mid point of WDM channel grid 501-505, and as by shown in the sampling symbol 515, wherein the signal component of WDM channel has the lowest spectrum power density, is approximately-48dB with respect to the peak power density of example shown in being used for; This is corresponding to the upper limit～45dB of OSNR value, can through to shown in the noise samples of WDM signal measure, the other 3dB that has the signal power that records is used for explaining two of each noise samples point 515 near the interaction of interchannel.

If the estimative sample frequency of optical noise offsets from half grid positions, the very major part of signal component can be contained in the Noise Estimation that is obtained by sampling, thus dynamic range that restriction OSNR measures and the accuracy that is used for big OSNR value thereof.As an example, Fig. 8 b illustrates, if noise samples is from half grid positions (ν _n+ Δ _Ch/ 2) 515 depart from about 3GHz or about δ f/4, arrive new position 515 ', and then the dynamic range of OSNR measurement reduces similar 10dB.Similarly, Fig. 8 c illustrates, if about 6GHz or about δ f/2 are departed from noise position 515, arrives new position 515 ", then the dynamic range measured of OSNR reduces similar 20dB, and only be lower than the OSNR value of about 24dB can be by measurement reliably.When channel signal component further as when being different from spectrum, spreading shown in Fig. 8 a-8c, and sampling function T (f-f _{M, j}) finite width when being calculated, the decay of OSNR measuring accuracy and dynamic range will be more serious.

Therefore, quite little even sample frequency 515 departs from its optimum frequency position, also can seriously cause the dynamic range that OSNR measures and the degradation of accuracy; Minimum at said optimum frequency position signalling component, for example, when spectrum be symmetry and also when being the center with the channel grid, signal component is in the centermost of adjacent channel.

Therefore, another aspect of the present invention provides a kind of improved method, is used to use the OSNR of multiple-input and multiple-output dispersion element 101 monitoring input optical signal S; Through concentrating in the predetermined frequencies sampling location accurate noise samples and the data processing technique of using the estimation channel signal component with suitable accuracy are provided, this method has been eliminated aforementioned OSNR problems of measurement.Said method is based on observation (observation): use to have for example to surpass the sampling function of the finite width of the 5-10% channel separation typical WDM signal of sampling, such as the sampling function T (f-f of AWG101 _{M, j}), said sampling function preferably has slightly less than Δ _ChThe bandwidth b of/M, the sample spectrum that obtains comprises the quite wide peak that the signal component by said channel occupies, and has the trough that is rather narrow that is used for Noise Estimation in half grid positions left side, therefore about channel grid ν _nSample frequency f _{M, j}Accurate location, for obtaining accurate Noise Estimation than obtaining the channel signal power P _ChAccurate estimation much important.

Go back to Fig. 4; Be used to import the accurate OSNR monitoring of WDM signal S; The embodiment of OPM1 of the present invention have the designated optical noise component that is used for measuring input light WDM signal S 100 selections of M input port one of, for example shown in Fig. 4 N input port 100 _N, and M input port 100 other M-1 of the designated signal component that is used for measuring the WDM signal.

Therefore, J output port 110 is arranged to first group of J centre frequency { f} _M=N={ f _{N, j=1}, f _{N, j=2}..., f _Nj=JBe optically coupled to and be selected port one 00 _N, said centre frequency is with the channel frequency separation Δ _ChEvenly distribute, just have the Δ of being substantially equal to _ChThe first sample frequency Δ f ₁=(f _{N, j}-f _{N, j+1}), and with the channel frequency separation Δ _ChConstant predetermined amount mark q depart from channel frequency ν _n, said channel frequency separation Δ _ChDetection is used for the optical noise rank of WDM interchannel.This can realize that so that the difference of each output port 110 receiving inputted signals spectrum part, said input signal is according to sample frequency { f through first end 111 of suitably locating output port 110 along focal curve 160 _{N, j}In the group selected be the center with the different sample frequency.The simulation that can use a computer is confirmed preferably to confirm by means of suitable test, as those skilled in the art have known along the correct position of the end 111 of curve 160.

In operation, be coupled into selected input port 100 when importing the WDM signal _NThe time, J output port 110 cooperated with photodetector array 181, and the predetermined spectral position between WDM is used for detecting the spectral noise value at said spectral position, with J the power reading { S} that processor shown in Fig. 9 850 is provided to the spectrum sample of input signal _N={ S _{N, j}, j=1 ... J}, thus as stated, can confirm optical noise value P for WDM channel separately _N

The channel frequency separation Δ _ChConstant predetermined amount mark q be selected for and make at sample frequency f _{N, j}The signal component at place is minimum.As for typical WDM signal, these best spectral positions are channel frequency grid ν _n=(ν ₀+ n Δ _Ch), n=0,1 ... half grid positions, frequency ν just _{N ±} =ν _n+/-Δ _Ch/ 2/.Therefore, in the embodiment of OPM1, the channel frequency separation Δ _ChPredetermined portions at Δ _Ch/ 2-a and Δ _ChBetween/the 2+a, wherein, a is a predetermined frequencies tolerance parameter, like this with select be used for noise testing input port 100 _NThe J that is associated sample frequency f _{N, j}, j=1 ... J, in each be positioned in the centre of two adjacent channel frequencies with equidistance, preferably be no more than said predetermined low frequency tolerance parameter a with the deviation of said position, general for approximately or be lower than sampling interval δ f=Δ _Ch10% of/M, or 2GHz preferably approximately, and in most preferred embodiment approximately or be lower than 1GHz.

Because AWG 101 is thermally sensitive; So OPM 1 comprises the temperature sensor 120 that is preferably mounted on the PLC in addition; Wherein AWG 101 realizes being used to detect temperature wherein with switch 330 near AWG 101; And temperature controller 170, its temperature through the control dispersion element is to first group of J centre frequency { f at the predetermined spectral position place of WDM interchannel _{N, j=1}, f _{N, j=2}..., f _{N, j=J}Correct.

The M of AWG 101 input port 100 is arranged to second group of M centre frequency f _{M, j}Be optically coupled to select in J the output port one of,, wherein every two adjacent centre frequencies are with at least 2 Δs _Ch/ M, or by satisfying relationship delta _ChThe frequency interval of k/M separates, and wherein integer k>=2 are used to suppress the unnecessary coupling between the input port.

The M of AWG 101 input port 100 also is configured and is used at the individual frequency band T (f-f of J * (M-1) _{M, j}) in will be optically coupled to J output port, each is with the different sample frequency f _{M, j}Be the center, wherein, m ≠ N and j are changed to J from 1.Preferably, through contain concave surface slab (concave-slab) waveguide 140 at the interface suitably the end of location input Vernier port one 00 come it is configured so that one of J output port 110 at work, for example port one 10 _j, to satisfy second group of M centre frequency { f of equality (11) and (12) _{J ', m=1}, f _{J ', m=2}..., f _{J ', m=M}Be coupled to each port in M the input port 100,, wherein two the every adjacent frequencies in the centre frequency are with the frequency interval Δ _ChK/M is perhaps with at least 2 Δs _Ch/ M is spaced apart, integer k>=2 wherein, said at least 2 Δs _ChThe frequency interval of/M is used to suppress the unnecessary coupling between the input port 100.

Selection is used for the input port 100 of noise testing _NBe preferably the central port of M input port 100, if M=8 just, port one 00 _NBe preferably the 4th or the 5th port of eight input ports 100, but can be any port of input port 100.In certain embodiments, AWG 101 can have the input port more than M, but only uses the subclass of M input port at work.

Similarly, select to be used to dispose the output port 100 of M input port 100 _{J '}Be preferably one of center output port, for example,,, but can be any of output port 110 then corresponding to j=20 if 40 output ports 110 are arranged.

A kind of control circuit of Fig. 9 schematic illustration, it can be used to control the operation of OPM1 of the present invention.Processor unit 850 so that the DSP form occurs can be stored and process information, and said information is surveyed by J photodetector of the photodetector array that is provided 181; It equally also can adopt the FPGA of suitable programming, a kind of general purpose microprocessor, or outer computer.The operation of electric controller 802 control Vernier switches 330 forms together and is configured to the control device that receives input optical signal, is used for to each M input port of AWG 101 input optical signal being provided in regular turn through OPM port 810.

Vernier switch 330 is in response to from the control signal stepping of electric controller 802 M input port through dispersion element 101, thereby with input optical signal an input port in the highest flight is provided to the dispersion element 101 at every turn.

In each step, J power reading of photodiode array 181 output as said above in this specification, provides with one group of J frequency { f} _mInput signal information, and these power readings are passed to Digital Signal Processing (DSP) unit 850 through analog-to-digital converter 840.Said DSP unit has electrical storage, wherein one group J power reading { S} _mWith J centre frequency or sample frequency { f} _mA class frequency separately in each step, be stored.The operation of electric controller 802 and temperature controller 170 is also controlled in DSP unit 850, receives the temperature reading from temperature sensor 170 simultaneously.

When input optical signal one of was coupled in M the input port 100, DSP 850 was programmed the noise level that is used for confirming according to the signal of telecommunication at least one channel of WDM channel, and the said signal of telecommunication is represented the power reading S that receives from photodetector device 181 _{M, j}And when input optical signal is coupled into all the other M-1 of M input port 100 in regular turn, use data processing algorithm according to the optical signal power of confirming to be used at least one WDM channel from the signal of telecommunication of J photodetector reception.

More specifically, DSP 850 is programmed the power reading of handling storage with the calibration information that uses pre-stored, confirming to exist in the input optical signal OSNR of at least one in the WDM channel, through execution in step:

A) use N input port 100 in M the input port 100 that is coupled to selection _NInput optical signal, the power reading { S} of the storage that handle to obtain _N, with confirm with the WDM channel at least one optical noise value P that is associated _N

B) use the input optical signal that is coupled to remainder in M the input port, handle the power reading { S} of the storage that obtains _m={ S _{M, j}, m=1 ..., M, j=1 ..., J}, m ≠ N, with confirm with the WDM channel at least one optical signal value P that is associated _SAnd,

C) use respectively in step (a) and the optical signal value P of acquisition (b) _SWith optical noise value P _N, calculate said at least one the OSNR value in the said WDM channel.

Step (b) can comprise the power reading S that uses predetermined these storages of look-up table identification _{M, j}Step; In the power reading of said storage and the WDM channel said at least one be associated, said look-up table with in M the position of switch 330 each with J the photodetector that comes from photodetector array 181 in each respectively with centre frequency f _{M, j}Each be associated.Said look-up table also can comprise and depend on centre frequency f _{M, j}The information of temperature correlation, temperature reading is provided by temperature sensor 120.Use for example peak recognizer, optical signal value P _SCan basis confirm with at least one power reading that is associated described in the WDM channel.

Significantly, abovementioned steps can be used to calculate the OSNR that is present in each WDM channel in the input optical signal.

In one embodiment; OPM1 is by precorrection; For example through using known input optical signal; Pass through each input port stepping input signal of dispersion element 101 in regular turn, and gather signal, and corrected value is stored in the DSP memory from the photodetector of photodetector array 181 in each step.Passband T (f-f about dispersion element 101 _{M, j}) shape and the information of width, and centre frequency f _MjThe value of measurement also be used as correction data and be stored in the memory, during said at work correction data is used to handled by the numerical value of photodetector output.Device 1 also can be corrected with temperature.

As an example, Figure 10 a and 10b explain the OSNR method for supervising that uses OPM1 according to the present invention, and AWG 101 has M=4 input port and 40 output ports, is used for the WDM signal on the 50GHz ITU grid.Black rhombus representes to compose sampled point, and said spectrum sampled point is according to the sample frequency grid { f among the AWG 101 _{M, j}On frequency, locate.Output port is configured to so that when input light was coupled in four input ports 100 the 2nd, output port 110 received with 40 sample frequency { f _2,1..., f _2,40In first group of { f} _M=2Be the discrete spectrum part of the input light at center, said sampling is { f frequently _2,1..., f _2,40With the channel separation Δ _Ch=-0.5GHz evenly distribute.Then, AWG 101 is by temperature adjustment, with 40 sample frequency { f _2,1..., f _2,40With the intermediate point position ν of 50GHz ITU grid _N+1/2Align, as by the sampling symbol 615 shown in.Input port 100 be configured so that at input light when between them, being changed, the center in 40 output port 110 arrays for example the 20 output port receives with second group of M=4 sample frequency { f _1,20..., f _4,20Be the spectra part at center, said sample frequency { f _1,20..., f _4,20Spaced apart with frequency 25GHz, 37.5GHz and 25GHz, f just _2,20=f _1,20-25GHz, and f _3,20=f _1,20-62.5GHz, f _4,20=f _3,20-87.5GHz.

The configuration of the input and output port of AWG 101 produces sample frequency grid { f _{M, j}, it generally is periodic on the centre of the sample spectrum that is provided by the center output port, for example has 15＜j＜25, like F among illustrated this embodiment that is illustrated in OPM1 of Figure 10 a _J3 adjacent WDM channels 620,630 of the centre of=2THz operating frequency range and 640, and a series of general periodic samples periodic point 615,625,635,645 etc.

Yet, sampling grid { f _{M, j}As by several first or the end of the sampling spectrum that provides of last output port 110 for example become irregular on j≤5 and j>=35; Just aperiodic; As illustrated among Figure 10 b; Be illustrated in 3 adjacent WDM channels 820,830 and 840 that the edge is other in the 2THz operating frequency range, for example provided by first group of 4 output port 110.

Therefore, a plurality of centre frequency { f _{M, j}Comprise and be dispersed in whole sampling grid { f _{M, j}On first group of sample frequency { f _2,1..., f _2,40615, said sample frequency is generally and is evenly separated, and departs from the target location that they are positioned at adjacent channel frequency middle part just and be less than predetermined frequency tolerance value a, for example is less than 2GHz, and preferably is less than 1GHz; Simultaneously, a plurality of centre frequency { f _{M, j}Also comprise M at least the sequence of centre frequency continuously; The shown sample frequency sequence of black diamonds among Figure 10 b for example; Wherein, because input port relies on the spatial dispersion characteristic D of dispersion element 101, the frequency interval between the centre frequency of adjoining changes greater than predetermined quantity.For example, possibly represent sample frequency f _{M=2, j=3}Sampled point 835 depart from the frequency offset 611 of the about 3GHz of target grid positions separately, this frequency offset has surpassed predetermined frequency shift (FS) threshold value a, is 2GHz in this example.

(M-1)=3 a sampled point 845,835 and 825 can be used for estimating the signal strength signal intensity in the channel 840, for example through using the peak match algorithm of the shape of supposing predetermined signal peak 820,830,840 grades.If frequency offset 611 is no more than target sample frequency δ f=Δ at interval _Ch/ M's is about 30% to 40%, or is no more than about 5GHz for the example that illustrates, and this estimation can have enough accuracy.Advantageously; This noise estimates that this sample frequency 615 is in the frequency that is positioned at predetermined optimum position between equidistant channel 820,840 grades through using sample frequency 615 to accomplish; Said channel 820; Therefore optimum position between 840 grades with the for example about 1GHz of pinpoint accuracy more or still less causes suitable accurate noise to be estimated, thereby compared with prior art can accomplish accurate OSNR monitoring with the increased dynamic scope.

Though AWG has some advantage as the embodiment of dispersion element 101, dispersion element 101 also can be for example body blazed grating, holographic grating, volume phase grating.Supervising device 181 can be photosensitive optoelectronic device discrete or array, comprises but is not limited to photodiode and photo-thermal electronic device or charge coupled device.Switch 330 also can be optical switch, slab guide switch or the MEMs switch of machinery.

In a word; The present invention provides a kind of optical performance monitor; Be used for accurately monitoring the OSNR of input light WDM signal, and the correlation technique of monitoring OSNR, said optics major part can be integrated in the single LPC chip that is connected with photodiode array by monolithic; And they do not have tunable filter, the control circuit that need not be correlated with.Use the AWG that combines with switch with M Vernier input port and J output port; Be used to cycle through M Vernier input port; With than using the almost big M of single input AWG frequency doubly on M times of dense frequencies grid, can monitor input signal, the OSNR monitoring performance of enhancing is provided simultaneously.

Certainly do not break away from and also can imagine other many embodiment in aim of the present invention and the scope.

Claims (11)

1. optical performance monitor is used to monitor the OSNR OSNR of the input optical signal that comprises many wave division multiplexing WDM channels, and said WDM channel has with the channel frequency separation Δ _ChEqually distributed channel center frequency, said optical performance monitor comprises:

Dispersion element comprises M input port and J output port, M＞2 and J＞2 wherein,

Control device is used for receiving input optical signal said input optical signal sequentially is optically coupled into each input port of M input port;

Photodetector device, said photodetector device and J output port optical coupling is used for when input optical signal is coupled into arbitrary port of M input port, providing the relevant signal of telecommunication of luminous power in each port with J output port; And

Processing unit, the signal of telecommunication that being used for basis is provided by said photodetector device is confirmed the OSNR of input optical signal;

Wherein dispersion element is used for position according to input and output port separately with the optical coupling of different sample frequency with each input port and each output port; Be used for when input optical signal is coupled into M input port in regular turn, the spectrum of input optical signal being sampled with a plurality of sample frequencys

A wherein said J output port is configured for first group of J sample frequency and one of will be optically coupled in M the input port, and said first group of J sample frequency is with the channel frequency separation Δ _ChBy even distribution and with the channel frequency separation Δ _ChPredetermined score depart from channel center frequency, be used to detect in the light of the WDM interchannel rank of making an uproar;

Wherein M input port is configured for second group of M sample frequency and one of will be optically coupled in J the output port, and wherein said second group of M sample frequency is with at least 2 Δs _Ch/ M interval, and,

Wherein dispersion element is characterised in that the spatial dispersion characteristic depends on input port and changes; And wherein a plurality of sample frequencys comprise a sequence of M continuous sample frequency at least; Wherein depend on the spatial dispersion characteristic of dispersion element because of input port, channel frequency separation is to change greater than predetermined value between the neighbouring sample frequency.

2. according to the described optical performance monitor of claim 1, wherein described processing unit programming is used for

When input optical signal one of is coupled in M the input port, confirm the noise level of at least one WDM channel according to the signal of telecommunication that receives from photodetector, and

When input optical signal is coupled in M the input port all the other M-1 in regular turn, use data processing algorithm to confirm the optical signal power of at least one WDM channel according to the signal of telecommunication that receives from J photodetector.

3. according to the described optical performance monitor of claim 1, a wherein said M input port be configured to through with one or more said second group of M sample frequency with said channel frequency separation Δ _ChOr its harmonic wave skew channel center frequency, said second group of M sample frequency is plotted in Δ _ChOn the periodic sequence of the isolated M an of/M sample frequency.

4. according to the described optical performance monitor of claim 3, wherein said second group of M sample frequency is less than two channel frequency separation Δs _ChFrequency range in.

5. according to the described optical performance monitor of claim 1, channel frequency separation Δ wherein _ChPredetermined score at Δ _Ch/ 2-a and Δ _ChBetween/the 2+a, wherein a is a preset frequency tolerance parameter.

6. according to any one described optical performance monitor in the claim 1 to 5, also comprise temperature controller, be used for through control dispersion element temperature to calibrate first group of J sample frequency at the predetermined spectral position of WDM interchannel.

7. according to any one described optical performance monitor in the claim 1 to 5, wherein said dispersion element comprises array waveguide grating AWG.

8. method that is used to monitor the OSNR OSNR of input optical signal, said input optical signal comprises many wave division multiplexing WDM channels with channel center frequency, said channel center frequency is with the channel frequency separation Δ _ChEvenly distributed, said method comprises step:

A) dispersion element that comprises M input port and J output port, wherein M＞2 and J＞2 are provided;

B) J output port of configuration is used for will being optically coupled to selecteed one of M input port with first group of J sample frequency, and said sample frequency is with the channel frequency separation Δ _ChEvenly distributed, and departed from Δ from channel center frequency _Ch/ 2;

C) M input port of configuration is used for so that J * (M-1) individual different sample frequency will be optically coupled to J output port, so that in operation with by at least 2 Δs _ChIsolated second group of M the sample frequency of/M will be from each port in the said M input port that is optically coupled to one of in the said J output port;

D) input optical signal is coupled into described in M the input port of dispersion element selecteed one;

E) use detection of optical power in photo-detector each in J output port, to obtain J power reading and they are stored in memory cell;

F) in regular turn input optical signal is coupled into each in all the other M-1 input port in the dispersion element, each repeating step e);

G) the power reading that handle to use input optical signal to obtain, said input optical signal are coupled into described in M the input port selecteed one, to confirm to be used for the optical noise value of at least one WDM channel;

H) the power reading of the storage of input optical signal acquisition is used in processing, and said input optical signal is coupled into remainder in M the input port, to confirm to be used for the optical signal value of at least one WDM channel; And,

I) use at step g) and h) in the light signal separately and the optical noise value that obtain, calculating is used for the OSNR value of at least one WDM channel.

9. according to the described method that is used to monitor OSNR of claim 8, wherein step c) comprises M the input port in location, one or more with said channel frequency separation Δ through with in second group of M sample frequency _ChOr its harmonic wave skew channel center frequency, so that said second group of M sample frequency can be plotted on the periodic sequence of M sample frequency, a said M sample frequency is with Δ _Ch/ M is spaced apart.

10. according to the method that is used to monitor OSNR of claim 8 or 9, wherein said dispersion element comprises array waveguide grating AWG.

11., further comprising the steps of according to the method that is used to monitor OSNR of claim 8 or 9:

Use predetermined look-up table, be identified in the power reading that step e) obtains, said power reading and at least one WDM channel-associated,

Step h wherein) comprises and use the peak recognizer, according to confirming optical signal value with the power reading of at least one WDM channel-associated.

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