JP4825128B2 - Optical amplification device and optical communication system - Google Patents

Description

  The present invention relates to an optical amplifying device including a low-speed optical amplifier having a low response speed and a high-speed optical amplifier having a high response speed, and an optical communication system using the optical amplifying device.

  In a conventional optical amplifying apparatus, in order to modulate and transmit monitoring control information as a signal, for example, as described in Non-Patent Documents 1 and 2, an EDFA (Erbium-) using an erbium-doped fiber as an amplifying medium is used. A method of modulating the intensity of carrier light by modulating the gain of a Doped Fiber Amplifier) is used. The EDFA provides a constant gain for compensating for loss and attenuation in an optical fiber through which carrier light propagates, and has a function of intensity-modulating a signal. Modulation of the gain of the EDFA is realized by modulating the intensity of the excitation light at a desired frequency.

  However, since the EDFA has a characteristic that the gain does not follow the modulation of the excitation light at a high frequency, even if the excitation light is modulated at a high frequency, the gain cannot be sufficiently modulated at a frequency of 1 MHz or more. Therefore, in EDFA, even if an attempt is made to modulate the gain at a high frequency in order to increase the speed of sending a large amount of information per unit time, it cannot be realized.

  In order to solve this problem, for example, if a Raman amplifier is used as described in Patent Document 1, the gain can be modulated at a high frequency by increasing the modulation frequency of the pumping light. However, a Raman amplifier has a lower amplification efficiency than an EDFA, and a high-intensity pumping light is necessary to provide a sufficient gain to compensate for a loss received by an optical fiber through which carrier light propagates. Can only have the function of intensity modulating the signal.

JP 11-344732 A

NTT R & D, Vol.43, No.11, 1994, P.1191-1195 K. Shimizu et al., "Supervisory signal transmission experiments over 10000km by modulated ASE of EDFAs," Electronics Letters, 10th, June, 1993, Vol. 29, No. 12

  Therefore, it is conceivable that the optical amplifying apparatus includes both an EDFA that gives a constant gain and a Raman amplifier that modulates the gain. In such a configuration, an excitation light source for the EDFA and a pump for the Raman amplifier are used. A light source is required, and the number of excitation light sources increases, resulting in a complicated device configuration, high costs, an increase in size of the device, an increase in power consumption, and a decrease in reliability.

  The present invention has been made in view of the above, and is capable of transmitting a high-speed signal while suppressing an increase in the number of excitation light sources that leads to an increase in power consumption, component cost, circuit mounting volume and a decrease in reliability. It is an object of the present invention to obtain an optical amplifying device that performs the above and an optical communication system using the optical amplifying device.

In the optical amplifying device according to the present invention, a constant gain is given to the all-wavelength carrier light of the input wavelength-multiplexed carrier light to output it, and the carrier light of some wavelengths of the wavelength-multiplexed carrier light the an optical amplifier device for intensity modulation and outputs, said carrier light with a wavelength of a wavelength-multiplexed carrier light ɽ all is inputted, with no follow-up is gain for the modulation of the excitation light with high frequency characteristics, A low-speed optical amplifier having a slow response speed, a demultiplexer for demultiplexing the wavelength-multiplexed carrier light output from the low-speed optical amplifier into carrier light of some wavelengths and carrier light of other wavelengths, and the demultiplexer A high-speed optical amplifier with a fast response speed, having a characteristic in which a carrier light of a part of the wavelength-multiplexed carrier light to be output is input and the gain follows the modulation of the high-frequency pumping light; Slow light A common pumping light source for supplying by distributing the excitation light gain wide device is intensity modulated at a high frequency which does not follow the slow-light amplifier and the high-speed optical amplifier, the other carrier wavelengths output from the demultiplexer A multiplexer that multiplexes light and carrier light of a part of the wavelength output from the high-speed optical amplifier, and the low-speed optical amplifier is substantially constant in time with the pump light. A gain is given to the carrier light, and the high-speed optical amplifier gives a gain modulated by the pumping light to the carrier light.

  According to the present invention, the low-speed optical amplifier for compensating for transmission loss and the signal modulation high-speed amplifier share the pumping light source, thereby enabling high-speed signal transmission, Power consumption, component cost, and circuit mounting volume are reduced, and reliability can be further improved.

FIG. 1 is a block diagram showing the configuration of the optical amplifying device of the first embodiment. FIG. 2 is a graph showing the characteristics of EDF gain modulation efficiency. FIG. 3 is a diagram showing a time waveform when the intensity of the excitation light is modulated. FIG. 4 is a diagram showing a distribution of signal power density with respect to frequency. FIG. 5 is a diagram showing another internal configuration example of the OADM. FIG. 6 is a diagram illustrating an internal configuration example of a common excitation light source of the optical amplification device according to the second embodiment. FIG. 7 is a diagram illustrating another internal configuration example of the common excitation light source of the optical amplifying device according to the second embodiment. FIG. 8 is a block diagram showing the configuration of the optical amplifying device of the third embodiment. FIG. 9 is a block diagram showing a configuration of the optical amplifying device according to the fourth embodiment. FIG. 10 is a block diagram showing the configuration of the optical amplifying device according to the fifth embodiment. FIG. 11 is a diagram illustrating an optical communication system according to a sixth embodiment configured using the optical amplifying devices according to the first to fifth embodiments. FIG. 12 is a block diagram showing a configuration of the optical amplifying device according to the seventh embodiment. FIG. 13 is a diagram illustrating an optical communication system according to an eighth embodiment configured using the optical amplification device according to the seventh embodiment.

  In order to explain the present invention in more detail, it will be described with reference to the accompanying drawings.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing an optical amplification apparatus according to Embodiment 1 of the present invention. The optical amplifying apparatus 1 includes a high-speed optical amplifier 2, a low-speed optical amplifier 3, a common pumping light source 4, a demultiplexer 5, and an optical add-drop module (OADM) 6.

  The optical amplifying apparatus 1 according to the first embodiment gives a constant gain to a carrier signal of all wavelengths of input wavelength multiplexed carrier light and outputs it, and also outputs carrier light of some wavelengths of the wavelength multiplexed carrier light. The low-speed optical amplifier 3 that gives a constant gain to the carrier signals of all wavelengths, and the high-speed optical amplifier 2 that modulates the intensity of the carrier light of some wavelengths and outputs it. By using the excitation light source 4 in common, the device is made more reliable, lower in cost, and smaller in size.

  The common pumping light source 4 is a pumping light source common to the high-speed optical amplifier 2 and the low-speed optical amplifier 3, and includes a pumping LD (pumping laser diode) 17 and a multiplexer (coupler) 18. In this case, two pumping LDs that output pumping light are provided, and the output light is multiplexed by the multiplexer 18. A pumping LD (pumping laser diode) 17 drives the pumping LD using the modulation signal to directly change the intensity of the light source by changing the modulation signal, or modulates the output light from the pumping LD 17 from the outside. By using an external modulation method that applies the above, the pumping light intensity-modulated at a high frequency (for example, 1 MHz or more) that the gain of the low-speed optical amplifier 3 does not follow is generated. As the multiplexer 18, for example, a wavelength multiplexer that multiplexes light having slightly different wavelengths may be used, and the wavelengths of the two pumping LDs 17 may be slightly different. Further, as the multiplexer 18, a polarization beam combiner that combines two orthogonally polarized light beams orthogonal to each other may be used.

  The demultiplexer 5 bisects the pumping light output from the common pumping light source 4 and inputs each pumping light to the low-speed optical amplifier 3 and the high-speed optical amplifier 2 via the fibers 500 and 501, and the low-speed optical amplifier 3 and the high-speed optical amplifier 2. In the optical amplifier 2, a gain is given to the carrier light.

  The low-speed optical amplifier 3 is an optical amplifier with a low response speed, and in this case, is realized by an EDFA. The low-speed optical amplifier 3 includes an erbium-doped optical fiber (EDF) 13, a WDM multiplexer 14, an isolator (ISOlator) 15, and a gain equalizer (Gain EQualizer) 16. The isolator 15 is for stabilizing the apparatus by preventing the backflow of the carrier light amplified by the EDF 13. The gain equalizer 16 has a transmission characteristic for correcting the wavelength characteristic of the EDF 13 and is used to align the intensities of wavelength-multiplexed carrier light. The isolator 15 and the gain equalizer 16 are inserted as necessary.

  The pumping light from the common pumping light source 4 modulated at a high frequency is guided to the optical fiber through which the carrier light propagates by the WDM multiplexer 14 and gives a gain to the carrier light by the EDF 13. Wavelength multiplexed carrier light is input to the EDF 13 via the input point 100. In this example, the EDF 13 employs a backward pumped EDFA in which the pump light and the wavelength multiplexed carrier light propagate in opposite directions. The EDF 13, which is an amplification medium doped with erbium ions, has a characteristic that the gain is not modulated when the excitation light is modulated at a high frequency due to the characteristic of erbium ions. Therefore, in this case, the pump light from the common pump light source 4 modulated at a high frequency only gives a constant gain that does not change with time to the wavelength multiplexed carrier light, and its intensity is not modulated.

  FIG. 2 shows the EDF gain modulation efficiency characteristics of a typical EDFA, with the EDF excitation light modulation frequency on the horizontal axis and the EDF gain modulation efficiency on the vertical axis. “EDF gain modulation efficiency” is an amount indicating how much the gain is modulated when the intensity of the pumping light is modulated with a certain amplitude. FIG. 2 shows that the gain amplitude in the case of modulation at a low frequency of 100 Hz or less is set as a reference (0 dB), and the modulation amplitude of the gain decreases as the modulation frequency increases. When the modulation frequency is 1 MHz, the EDF gain modulation efficiency is −30 dB or less, that is, 1/1000 or less, so that the gain is modulated only to 1/1000 or less during the low-speed modulation, and the gain is substantial. It becomes a constant value that does not change over time. FIG. 3 shows an example of a time waveform when the intensity of the excitation light is modulated with the modulation width 201. From the above, in the EDF 13, the excitation light has a constant excitation light intensity with an average intensity 200 in the figure. As a result, substantially the same gain is given.

  The high-speed optical amplifier 2 is an optical amplifier with a high response speed. In this case, the high-speed optical amplifier 2 is realized by a forward pumping Raman amplifier in which pumping light and carrier light propagate in the same direction. The high-speed optical amplifier 2 includes a WDM multiplexer 10, a Raman fiber 11, and a pumping light removal filter 12. As will be described later, a part of the wavelength multiplexed carrier light of the wavelength-multiplexed carrier light is input to the high-speed optical amplifier 2 via the optical fiber 502 by the OADM 6.

  The pumping light from the common pumping light source 4 modulated at a high frequency is combined with carrier light having a partial wavelength from the optical fiber 502 by the WDM multiplexer 10 and input to the Raman fiber 11. The pumping light gives a modulated gain to the carrier light having a part of the wavelength in the Raman fiber 11. For example, as shown in the document “2002 Proceedings of Communication Society Conference 2002-10-107”, the gain of the forward pumping Raman amplifier can be modulated at a high frequency by modulating the pumping light, Suitable as a high-speed optical amplifier. On the other hand, in the backward pumped Raman amplifier in which the carrier light and the pump light propagate in the opposite directions through the Raman fiber, the gain does not follow when the pump light is modulated at a high frequency, like the EDFA. The gain cannot be modulated with frequency, and is not suitable for a high-speed optical amplifier.

  The carrier light that has received the gain modulated by the Raman fiber 11 is output to the optical fiber 503 through the pumping light removal filter 12. The excitation light removal filter 12 has a characteristic that does not transmit excitation light, and prevents unnecessary excitation light from being output from the high-speed optical amplifier 2. The excitation light removal filter 12 is arranged as necessary.

  The OADM 6 includes a demultiplexing unit 19 and a multiplexing unit 20, and extracts and demultiplexes only a part of the wavelength of the wavelength multiplexed carrier light output from the low-speed optical amplifier 3 by the demultiplexing unit 19. Then, the light is guided to the optical fiber 502, and light of other wavelengths is output to the multiplexing means 20. The multiplexing unit 20 multiplexes the wavelength multiplexed carrier light input from the demultiplexing unit 19 and the partial wavelength carrier light input from the high-speed optical amplifier 2, and outputs them to the output point 101.

The OADM 6 is realized by a component such as a dielectric multilayer filter having a desired wavelength characteristic, for example. The OADM 6 is also realized by a configuration as shown in FIG. The OADM 6 shown in FIG. 5 includes a fiber grating 21 and circulators 22 and 22 ′. The fiber grating 21 has a characteristic of reflecting only light of a specific partial wavelength and transmitting light of other wavelengths. The carrier light incident from the optical fiber 504 passes through the circulator 22 and is input to the fiber grating 21, and a part of the wavelength light is reflected and input to the circulator 22 again. From the characteristics of the circulator, the reflected light is output to the optical fiber 502 as shown by the arrow. Light of other wavelengths passes through the fiber grating 21 and the circulator 22 ′ and is output to the optical fiber 505. When light having the same wavelength as the light output to the optical fiber 502 is input to the optical fiber 503, the light reaches the fiber grating 21 from the circulator 22 ′, is reflected, and is input to the circulator 22 ′ again, to the optical fiber 505. Is output.
Thus, the fiber grating 21 contributes to both multiplexing and demultiplexing. Here, the two fiber gratings 21 are connected in series in order to completely reflect light having a wavelength to be reflected. Even if it is not completely reflected by one fiber grating, it is reflected by the second fiber grating, so that it is possible to prevent unintentional transmission. When sufficient reflection characteristics can be obtained with one fiber grating, two are not necessarily required. If two fiber gratings are not sufficient, three or more may be connected in series.

  Next, the operation will be described. The pumping light modulated at a high frequency and output from the common pumping light source 4 is divided into two by the branching filter 5 and input to the low-speed optical amplifier 3 and the high-speed optical amplifier 2 through the optical fibers 500 and 501, respectively.

  On the other hand, wavelength-multiplexed carrier light is input to the low-speed optical amplifier 3 via the input point 100. Since the pump light modulated at a high frequency is input from the common pump light source 4 to the low-speed optical amplifier 3, the gain does not follow the pump light and does not change with time in the EDF 13, as described above. A constant gain is given to the wavelength multiplexed carrier light.

  Most of the wavelength multiplexed carrier light given a constant gain by the low-speed optical amplifier 3 passes through the OADM 6 and is output from the output point 101. The carrier light of a part of the wavelength multiplexed carrier light to which a constant gain is given by the low-speed optical amplifier 3 is selectively extracted and demultiplexed by the OADM 6, and the high-speed light is transmitted through the optical fiber 502. Input to the amplifier 2.

  In the high-speed optical amplifier 2, the gain is modulated at a high frequency by the pumping light modulated at a high frequency input from the common pumping light source 4. It is input to the OADM 6 through 503. In the OADM 6, the intensity-modulated carrier light input via the optical fiber 503 is wavelength-multiplexed with the carrier light of other wavelengths and output via the output point 101.

  Thus, according to the optical amplifying apparatus 1, the carrier light having a wavelength passing through the high-speed optical amplifier 2 is intensity-modulated, but the carrier light having a wavelength other than that is not intensity-modulated and only a certain gain is given. It will be.

  In addition, it is desirable to use the pumping light whose intensity is modulated with a signal that is subcarrier-modulated at a high subcarrier frequency of 1 MHz or higher. That is, as a result of modulating the pumping light, if the pumping light contains a low frequency component, the gain of the low-speed optical amplifier 3 is modulated by the low frequency component, and the gain is not constant. For example, the graph of FIG. 4 (a) shows an example of the distribution of the signal power density with respect to the frequency. In this case, a low frequency component near the frequency zero exists. If baseband modulation for intensity-modulating such a signal as it is to the pumping light is performed, the gain of the low-speed optical amplifier 3 is modulated to some extent. Therefore, by setting a high subcarrier frequency of 1 MHz or higher and performing subcarrier modulation in which intensity modulation is performed with a sine wave signal of that frequency, the power density distribution becomes as shown in FIG. Ingredients can be eliminated. Thus, the gain of the low-speed optical amplifier can be made constant by intensity-modulating the excitation light with a signal that has been subcarrier-modulated at a high subcarrier frequency of 1 MHz or higher.

  As described above, in the optical amplifying apparatus 1 according to the first embodiment, excitation in an optical amplifying apparatus using two optical amplifiers having different response speeds, which includes a high-speed amplifier for intensity-modulating the gain and a low-speed amplifier for giving a constant gain. The light source is shared.

  Incidentally, when the pumping light sources of the low-speed optical amplifier and the high-speed optical amplifier are independent and each has one pumping LD, pumping is performed for the corresponding optical amplifier when one of the pumping LDs fails. Light is not supplied at all, and the function of the optical amplifying device cannot be maintained. Therefore, in order to improve the reliability, it is conceivable to provide two pumping LDs in the pumping light source of each optical amplifier, but a total of four pumping LDs are required, and the number of parts increases.

  On the other hand, in the configuration of the first embodiment, even if one of the pumping LDs 17 breaks down, half of the intensity of the pumping light is supplied to both the low-speed optical amplifier 3 and the high-speed optical amplifier 2. A certain level of function can be maintained. Therefore, if the excitation light source is shared as in the first embodiment, a highly reliable optical amplification device can be obtained. In other words, a highly reliable optical amplifying device can be realized with a small number of pumping LDs.

  Further, in the invention of Embodiment 1, when sufficient excitation light intensity and reliability can be obtained with one excitation LD, the excitation LD 17 in FIG. 1 can be reduced to one, It is possible to simplify the configuration, reduce the number of parts, and reduce the cost.

  If the range of 1450 to 1470 nm is used as the wavelength of the pumping light, both EDFA and Raman amplifier can give a gain to carrier light having a wavelength of around 1540 to 1560 nm, which is convenient.

  As described above, according to the first embodiment, the pumping light source is shared in the optical amplifying apparatus using the two optical amplifiers having different response speeds including the high-speed amplifier for intensity-modulating the gain and the low-speed amplifier for giving a constant gain. Thus, high-speed signal transmission can be performed, power consumption, component cost, and circuit mounting volume can be reduced, and reliability can be further improved.

  In the above description, the multiplexer 18 and the demultiplexer 5 of the common excitation light source 4 are described as independent forms, but these may be realized by one multiplexer / demultiplexer. For example, if an optical coupler having two ports for both input and output is used as a multiplexer / demultiplexer, multiplexing and demultiplexing are possible with one optical coupler. In addition, as the pumping light source used for the common pumping light source 4, only the case of the LD is shown, but other means may be used, for example, a solid laser, an optical fiber laser, or the like may be used.

Embodiment 2. FIG.
A second embodiment of the present invention will be described with reference to FIGS. In the first embodiment, the number of pumping LDs included in the common pumping light source 4 is two. However, in the embodiment, the common pumping light source 4 includes four pumping LDs.

  In FIG. 6, the output lights of the four pumping LDs 17 are multiplexed by a multiplexer 18 ′. A wavelength multiplexer or the like can be used as the multiplexer 18 ′.

  In FIG. 7, two of the four pumping LDs 17 are combined by a polarization beam combiner 18 ″ and then combined by a multiplexer 18. When the polarization beam combiner 18 ″ is used, the number of components is increased as compared with the case of FIG. 6, but non-polarized excitation light with no polarization polarization can be obtained. If the pump light is non-polarized light, the gain of the Raman amplifier can eliminate the polarization dependence depending on the polarization of the signal light, so that a stable gain can be obtained, and the forward pump Raman amplifier of the high-speed optical amplifier 2 can be obtained. Can stably modulate the signal light.

  In the configuration of FIGS. 6 and 7 using four pumping LDs 17, even if one of the pumping lights breaks down, both the low-speed optical amplifier 3 and the high-speed optical amplifier 2 have pumping light of three-quarter intensity. Therefore, the amount of gain reduction due to failure can be suppressed to a small level. Even when two or three pumping LDs 17 fail, the pumping light having half or one quarter intensity is supplied to both optical amplifiers, so that the minimum function can be maintained.

Embodiment 3 FIG.
Embodiment 3 of the present invention will be described with reference to FIG. In the third embodiment, a forward pumped EDFA in which pumping light and carrier light propagate in the same direction is used as the low-speed optical amplifier 3. Except this, it is the same as that of the first embodiment, and redundant description is omitted.

  In this configuration, the pump light modulated at a high frequency and inputted from the common pump light source 4 through the duplexer 5 and the optical fiber 500 is guided to the optical fiber through which the wavelength multiplexed carrier light propagates by the WDM multiplexer 14. The EDF 13 gives a gain to the carrier light. Also in this forward pumped EDFA, as in the case of FIG. 1 using the backward pumped EDFA, the pumping light modulated at a high modulation frequency is inputted from the common pumping light source 4, so that the carrier light is temporally Only a constant gain that does not change is given, and its intensity is not modulated.

Embodiment 4 FIG.
Embodiment 4 of the present invention will be described with reference to FIG. In the fourth embodiment, as the low-speed optical amplifier 3, a backward pumped Raman amplifier in which pumping light and carrier light propagate in opposite directions is used. Except this, it is the same as that of the first embodiment, and redundant description is omitted.

  In this configuration, pump light modulated at a high frequency and input from the common pump light source 4 via the duplexer 5 and the optical fiber 500 is transmitted to the optical fiber through which the wavelength multiplexed carrier light propagates in the WDM multiplexer 14. Then, the Raman fiber 13 'gives a certain gain to the carrier light.

  As described above, for example, the carrier light and the pumping light propagate in the opposite directions in the Raman fiber as shown in the document “2002 Proceedings of the Communications Society Conference 2002 B-10-107”. The backward pumped Raman amplifier, like the EDFA, has a characteristic that does not follow the modulation of the pump light at a frequency with a high gain, and therefore can be used as a low speed optical amplifier. In this case, as a characteristic unique to the Raman amplifier, a gain can be given with lower noise than that of the EDFA.

  In the case of the EDFA, the wavelength of the carrier light capable of giving a gain is limited to the vicinity of 1530 to 1590 nm. However, by using the Raman amplifier for the low-speed optical amplifier 3, the wavelength of the carrier light is changed to other wavelength bands. It is also possible to choose.

Embodiment 5 FIG.
A fifth embodiment of the present invention will be described with reference to FIG. In the first embodiment, the low-speed optical amplifier 3 is arranged on the upstream side of the flow of the carrier light, arranged on the downstream side of the high-speed optical amplifier 2, and the carrier light of all wavelengths is input to the low-speed optical amplifier 3. A part of the carrier light output from the low-speed optical amplifier 3 is configured to be input to the high-speed optical amplifier 2. However, the high-speed optical amplifier 2 is arranged upstream, and the low-speed optical amplifier 3 is arranged. May be arranged downstream. In other words, the carrier light may be input to the high-speed optical amplifier 2 before being input to the low-speed optical amplifier 3.

  In the configuration shown in FIG. 10, the demultiplexing means 19 inputs a part of the wavelength-multiplexed carrier light input from the input point 100 to the high-speed optical amplifier 2 and the other wavelengths. Are input to the low-speed optical amplifier 3. The output light from the low-speed optical amplifier 3 and the output light from the high-speed optical amplifier 2 are combined by the combining means 20 and output to the output point 101. In this case, unlike the first embodiment, only a part of the wavelength-multiplexed carrier light is input to the low-speed optical amplifier 3.

Embodiment 6 FIG.
A sixth embodiment of the present invention will be described with reference to FIG. This Embodiment 6 shows the form of the optical communication system comprised using the optical amplification apparatus of said each embodiment.

  This optical communication system is modulated by a transmission device 104 that transmits wavelength-multiplexed carrier light, one or more optical amplification devices 1 described in the first to fifth embodiments, and an optical fiber cable 105 through which carrier light propagates. And a receiving device 106 that receives wavelength multiplexed carrier light including carrier light.

  The transmission device 104 transmits carrier light obtained by multiplexing carrier lights having a plurality of wavelengths to the optical fiber cable 105. As described in the first to fifth embodiments, the optical amplifying apparatus 1 gives a constant gain to the wavelength multiplexed carrier light, compensates for the loss received by the optical fiber cable 105, and reduces the intensity of the attenuated carrier light. In addition to recovery, it has a function of modulating and outputting the intensity of only a part of the wavelength of the wavelength-multiplexed carrier light. The receiving device 106 receives wavelength-multiplexed carrier light including modulated carrier light.

  In the above system, if the wavelengths of the carrier lights modulated by the plurality of optical amplifying devices 1 are made different, even if signals are modulated by the plurality of optical amplifying devices at the same time, no interference occurs, and the receiving device 106 And each signal can be received independently. That is, when a plurality of optical amplifying devices are connected to one optical fiber, when one optical amplifying device modulates a signal, another optical amplifying device simultaneously modulates the signal with the same frequency. In this case, since the signal is mixed, a plurality of optical amplifying devices cannot simultaneously modulate the signal, and the number of optical amplifying devices that can be modulated must always be limited to one.

  In this case, the optical amplifying apparatus 1 can transmit a signal at a high frequency of 1 MHz or higher. Therefore, the signal that can be transmitted to the receiving device 106 with one optical fiber cable 105 is 1 MHz or more per optical amplifying device and can be transmitted from a plurality of optical amplifying devices 1 at the same time. Compared to this, a lot of information can be sent per unit time. Further, as described above, since the optical amplifying device 1 has high reliability, high reliability can be obtained as the entire optical communication system.

Embodiment 7 FIG.
A seventh embodiment of the present invention will be described with reference to FIG. Uplink carrier light and downlink carrier light are input to the optical amplifying device 1 ′ according to the seventh embodiment. The optical amplifying device 1 ′ includes an input point 100 for uplink carrier light, an uplink carrier light, and an uplink carrier light. It has a line carrier light output point 101, a downlink carrier light input point 102, and a downlink carrier light output point 103. In addition, for processing uplink and downlink carrier light, one pair, that is, two high-speed optical amplifiers 2, low-speed optical amplifiers 3, and OADMs 6 are provided. However, only one common excitation light source 4 and duplexer 5 are provided as in the first embodiment. That is, pumping light is input to one pair of high-speed optical amplifier 2 and low-speed optical amplifier 3 for each pair of upstream and downstream carrier light processing by one common pumping light source 4. The functions of the high-speed optical amplifier 2, the low-speed optical amplifier 3, the common pumping light source 4, the OADM 6, and the like are the same as those in the first embodiment, and redundant description is omitted.

  The pumping light modulated at a high frequency and output from the common pumping light source 4 is demultiplexed into four by the demultiplexer 5, and is transmitted through the optical fibers 500, 501, 500 ', and 501' as low-speed light for uplink. The signals are inputted to the amplifier 3, the downlink low-speed optical amplifier 3, the uplink high-speed optical amplifier 2, and the uplink high-speed optical amplifier 2, and give gain to the carrier light respectively. As described above, in the low-speed optical amplifiers 3 and 3, a constant gain that does not change with time is given to the carrier light by the pump light, and in the high-speed optical amplifiers 2 and 2, the intensity of the carrier light input by the pump light is modulated. Will be.

  When the wavelength-multiplexed carrier light is input from the uplink input point 100, it is amplified by the uplink low-speed optical amplifier 3 and given a certain gain here. Most of the carrier light passes through the uplink OADM 6 and is output from the uplink output point 101. A part of the wavelength-multiplexed carrier light output from the low-speed optical amplifier 3 for the uplink is selectively extracted and demultiplexed by the OADM 6 for the uplink, and is transmitted from the optical fiber 502. It is input to the high-speed optical amplifier 2 for the line. After the carrier light is intensity-modulated by the high-speed optical amplifier 2 for the uplink, it is input from the optical fiber 503 ′ to the OADM 6 for the downlink, where it is wavelength-multiplexed with the downlink carrier light and output to the downlink Output to point 103.

  In this way, most of the uplink carrier light is not intensity-modulated and is given only a certain gain by the uplink low-speed optical amplifier 3 and is output to the uplink. After being intensity-modulated through the high-speed optical amplifier 2, it is output to the downlink.

  On the other hand, when wavelength-multiplexed carrier light is input from the downlink input point 102, it is amplified by the low-speed optical amplifier 3 for downlink, and given constant gain here. Most of the carrier light passes through the downlink OADM 6 and is output from the downlink output point 103. A part of the wavelength-multiplexed carrier light outputted from the low-speed optical amplifier 3 for the downlink is selectively extracted and demultiplexed by the OADM 6 for the downlink, and is transmitted from the optical fiber 502. The signal is input to the high-speed optical amplifier 2 for the line. After the carrier light is intensity-modulated by the high-speed optical amplifier 2 for the downlink, it is input from the optical fiber 503 to the OADM 6 for the uplink, where it is wavelength-multiplexed with the uplink carrier light, and the output point of the uplink 101.

  In this way, most of the downlink carrier light is not intensity-modulated and is given only a fixed gain by the low-speed optical amplifier 3 for the downlink and is output to the downlink. After being intensity-modulated through the high-speed optical amplifier 2, it is output to the uplink.

  As the common pumping light source 4, the form shown in FIG. 6 can be applied. At this time, if an optical coupler having four ports for both input and output is used as a multiplexer / demultiplexer, the single coupler can combine and demultiplex. Waves are possible.

Embodiment 8 FIG.
FIG. 13 shows a configuration of an optical communication system using the optical amplifying device of the seventh embodiment, and two systems of an uplink and a downlink are provided.

  This optical communication system includes a transmission device 104 that transmits wavelength-multiplexed uplink carrier light, a transmission device 104 ′ that transmits wavelength-multiplexed downlink carrier light, and the one to a plurality of components described in the seventh embodiment. An optical amplifying device 1 ′, an optical fiber cable 105 through which uplink carrier light propagates, an optical fiber cable 105 ′ through which downlink carrier light propagates, a receiving device 106 that receives wavelength-multiplexed uplink carrier light, It has a receiving device 106 ′ for receiving wavelength-multiplexed downlink carrier light and an observation device 107 connected to each optical amplifying device 1 ′.

  The transmission device 104 transmits carrier light obtained by multiplexing carrier lights having a plurality of wavelengths to the optical fiber cable 105 on the uplink. In the optical amplifying apparatus 1 ′, as described in the seventh embodiment, a constant gain is given to the wavelength multiplexed carrier light, the loss received by the optical fiber cable 105 is compensated, and the intensity of the attenuated carrier light is recovered. Output to the uplink optical fiber cable 105, modulate the intensity of only a part of the wavelength-multiplexed carrier light, and output to the downlink optical fiber cable 105 'in the reverse direction. .

  That is, the carrier light transmitted from the transmission device 104 and input to the optical amplifying device 'via the uplink optical fiber cable 105 and modulated is received by the reception device 106' via the downlink optical fiber cable 105 '. To. On the other hand, for carrier light having a wavelength that is transmitted from the transmitting apparatus 104 and input to the optical amplifying apparatus 1 ′ via the uplink optical fiber cable 105 and is given only a certain gain and is not modulated, the uplink light It is output to the fiber cable 105 and reaches the receiving device 106.

  Similarly, the transmission apparatus 104 ′ transmits carrier light obtained by multiplexing carrier lights of a plurality of wavelengths to the downlink optical fiber cable 105 ′. In the optical amplifying apparatus 1 ′, as described in the seventh embodiment, a constant gain is given to the wavelength division multiplexed carrier light, the loss received by the optical fiber cable 105 ′ is compensated, and the intensity of the attenuated carrier light is increased. Recover and output to the downlink optical fiber cable 105 ′, modulate the intensity of only a part of the wavelength-multiplexed carrier light, and output to the uplink optical fiber cable 105 in the reverse direction To do.

  That is, the carrier light transmitted from the transmission device 104 ′ and input to the optical amplifying device ′ via the downlink optical fiber cable 105 ′ is modulated, and the modulated carrier light is received via the downlink optical fiber cable 105 ′. 106. On the other hand, for carrier light having a wavelength that is transmitted from the transmission device 104 ′ and input to the optical amplification device 1 ′ via the downlink optical fiber cable 105 ′ and is given only a certain gain and is not modulated, the downlink To the receiving device 106 ′.

  In this way, only the carrier light modulated by the optical amplifying device 1 ′ is folded back to the optical fiber of the reverse line and sent back to the receiving device near the transmitting device. Even when 105 ′ is disconnected, the carrier light returned before the disconnection reaches the receiving apparatus, and the system function can be maintained. Furthermore, since the optical amplifying device 1 ′ according to the seventh embodiment is configured to simultaneously modulate and transmit signals on the uplink and downlink, if the disconnection location of the optical fiber cables 105 and 105 ′ is one, Since a signal modulated on either the uplink or the downlink can be transmitted and delivered to either the receiving device 106 or 106 ′, it has high reliability.

  In the optical communication system of FIG. 13, if the wavelengths of the carrier lights modulated by the plurality of optical amplifying devices 1 are made different, even if the signals are modulated by the plurality of optical amplifying devices at the same time, there is no interference, and reception The devices 106 and 106 'can demultiplex each wavelength and receive each signal independently. Further, in the optical communication system of FIG. 13, the signal that can be transmitted to the receiving device by one optical fiber cable 105 is 1 MHz or more per optical amplifying device, and is transmitted simultaneously from a plurality of optical amplifying devices. Therefore, more information can be sent per unit time than in the conventional method. Further, as described above, since the optical amplifying device 1 ′ has high reliability, high reliability can be obtained as an entire optical communication system.

  Furthermore, as shown in FIG. 13, when an observation device 107 for observing earthquakes, tsunamis, temperatures, etc. is connected to the optical amplification device 1 ′, the carrier light is modulated by the optical amplification device 1 ′ using the observed information as a signal, It is possible to realize a remote observation system that transmits to the receiving devices 106 and 106 ′. Further, when the optical fiber cables 105 and 105 ′ are submarine cables installed on the seabed, and the transmitters 104 and 104 ′ and the receivers 106 and 106 ′ are submarine cable systems installed on the land station, the unit A lot of seafloor observation information can be sent to land stations per hour, and a highly reliable seafloor observation cable system can be realized.

  As described above, the optical amplifying device according to the present invention is useful for a submarine cable system for transmitting optical signals and a submarine observation cable system for observing earthquakes, tsunamis, temperatures, and the like.

Claims (10)

This is an optical amplifying apparatus that gives a constant gain to all wavelength carrier light of input wavelength multiplexed carrier light and outputs it, and also modulates and outputs the intensity of some of the wavelength multiplexed carrier light. And
The wavelength carrier light of wavelength of the multiple carrier light ɽ all are inputted, has a characteristic that the gain does not follow the modulation of the excitation light with high frequency, and a slow response speed slow-light amplifier,
A demultiplexer for demultiplexing wavelength multiplexed carrier light output from the low-speed optical amplifier into carrier light of some wavelengths and carrier light of other wavelengths;
Said carrier light of some wavelengths of the demultiplexer and the wavelength-multiplexed carrier light output from is inputted, has a characteristic that the gain is follow the modulation of the excitation light with high frequency, high-speed response speed is fast An optical amplifier;
A common pumping light source that distributes and supplies pumping light intensity-modulated at a high frequency that the gain of the low-speed optical amplifier does not follow to the low-speed optical amplifier and the high-speed optical amplifier;
A multiplexer for multiplexing the carrier light of other wavelengths output from the duplexer and the carrier light of a part of wavelengths output from the high-speed optical amplifier;
The low-speed optical amplifier gives a constant gain to the carrier light that does not substantially change with time due to the pumping light, and the high-speed optical amplifier gives the carrier light a gain modulated by the pumping light. An optical amplification device.   The optical amplifier according to claim 1, wherein the low-speed optical amplifier is an EDFA using an erbium-doped fiber as an amplification medium, and the high-speed optical amplifier is a forward pumped Raman amplifier.   The optical amplifier according to claim 1, wherein the low-speed optical amplifier is a backward pumped Raman amplifier, and the high-speed optical amplifier is a forward pumped Raman amplifier.   The optical amplifying apparatus according to claim 1, wherein the wavelength of the excitation light is in a range of 1450 to 1470 nm.   2. The optical amplifying device according to claim 1, wherein a modulation frequency of the pumping light is 1 MHz or more.   6. The optical amplifying device according to claim 5, wherein the excitation light is intensity-modulated with a signal subcarrier-modulated to a frequency of 1 MHz or higher. A transmitter for transmitting wavelength division multiplexed carrier light;
1 to a plurality of optical amplifying devices according to claim 1, which receives wavelength multiplexed carrier light from said transmitting device and transmits wavelength multiplexed carrier light including modulated carrier light;
A receiving device for receiving wavelength-division multiplexed carrier light including carrier light modulated via the one or more optical amplifying devices;
An optical communication system characterized by being connected by an optical fiber cable. An optical amplifying apparatus that outputs a wavelength-division multiplexed uplink carrier light and downlink carrier light with a given gain and outputs a modulated light of a part of the carrier light,
A first low-speed optical amplifier having a slow response speed and having a characteristic that the gain does not follow the modulation of the high-frequency pumping light, and the carrier light of all wavelengths of the wavelength-multiplexed uplink carrier light is input;
A second low-speed optical amplifier with a slow response speed, in which carrier light of all wavelengths of wavelength-multiplexed downlink carrier light is input and the gain does not follow the modulation of high-frequency pumping light;
A first demultiplexer for demultiplexing wavelength-multiplexed uplink carrier light output from the first low-speed optical amplifier into carrier light of some wavelengths and carrier light of other wavelengths;
A second demultiplexer for demultiplexing wavelength-multiplexed downlink carrier light wavelength-multiplexed carrier light output from the second low-speed optical amplifier into carrier light of some wavelengths and carrier light of other wavelengths;
A part of the wavelength carrier light that is wavelength-multiplexed output from the first demultiplexer is input, and the gain follows the modulation of the high frequency pumping light, A first high-speed optical amplifier having a high response speed;
Of the wavelength multiplexed downlink carrier light output from the second demultiplexer, the carrier light of a part of the wavelength is input, and the gain follows the modulation with respect to the modulation of the high frequency excitation light, A second high-speed optical amplifier having a high response speed;
Distributing pump light intensity-modulated at a high frequency that does not follow the gain of the first and second low-speed optical amplifiers to the first and second low-speed optical amplifiers and the first and second high-speed optical amplifiers; A common excitation light source to be supplied;
A first multiplexer that combines the output of the first low-speed optical amplifier and the output of the second high-speed optical amplifier and outputs the result to the uplink;
A second multiplexer that combines the output of the second low-speed optical amplifier and the output of the first high-speed optical amplifier and outputs the result to the downlink;
The first and second low-speed optical amplifiers provide carrier light with a constant gain that does not change substantially in time with the pumping light, and the first and second high-speed optical amplifiers with the pumping light. An optical amplifying device characterized in that a modulated gain is given to carrier light. A first transmitter that transmits wavelength-multiplexed uplink carrier light;
A second transmitter for transmitting wavelength-multiplexed downlink carrier light;
9. The method according to claim 8, wherein the WDM carrier light from the first and second transmission devices is received, and the WDM carrier light including the modulated carrier light is output to the uplink and the downlink. A plurality of optical amplification devices;
A first receiver that receives wavelength multiplexed carrier light including carrier light modulated via the one or more optical amplifiers from an uplink;
A second receiving device for receiving wavelength-division multiplexed carrier light including carrier light modulated via the one or more optical amplifying devices from a downlink;
An optical communication system characterized by being connected by an optical fiber cable. An observation device that is connected to each of the one or more optical amplification devices and inputs observation information to each optical amplification device;
The optical communication system according to claim 9, wherein the optical amplifying device modulates carrier light having a part of wavelengths using observation information from the observation device.

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