JP4868995B2 - Polarization orthogonal multiplexed signal light regeneration apparatus and polarization orthogonal multiplexed signal light regeneration method - Google Patents

Description

  The present invention relates to a polarization orthogonal multiplexed signal light regenerating apparatus that regenerates a polarization orthogonal multiplexed signal and a polarization orthogonal multiplexed signal regeneration method that have deteriorated during transmission.

  In general, an optical signal transmitted through an optical fiber or the like needs to be reproduced by relaying an optical signal because of waveform degradation during long-distance transmission. 2R playback devices with a waveform shaping function and 3R playback devices with a retiming / identification playback function have been developed. Furthermore, as the transmission speed per channel becomes higher, an optical 2R reproducing device and an optical 3R reproduction that perform optical signal processing on an optical signal are being developed (see Patent Document 1). As shown in FIG. 9, the optical 3R regenerator separates a separated optical signal from an inputted optical signal, inputs the separated optical signal to a clock pulse extraction unit, generates a clock pulse signal, and generates the clock pulse signal. The optical signal is input to the optical signal reproducing unit 21 to reproduce the optical signal.

On the other hand, studies on polarization orthogonal multiplexed signals have been conducted, and since this polarization orthogonal multiplexed signal has a polarization state orthogonal to each bit, interference hardly occurs even at high speeds. It is possible to improve.
JP2001-249371

However, in general, the clock pulse extraction unit and the optical signal light regeneration unit for performing optical signal processing have polarization dependency that a good operation cannot be obtained depending on the polarization state such as the angle of the input polarization. Have. On the other hand, when a polarization orthogonal multiplexed signal propagates through an optical fiber, which is an optical propagation medium, the polarization state of the optical signal rotates due to pressure, vibration, and temperature changes that are generally the surrounding environment of the optical fiber. It fluctuates remarkably. For this reason, when extracting a clock pulse by optical signal processing or the like for a polarization orthogonal multiplexed signal, there is a problem that a good operation cannot be obtained depending on a clock pulse extraction unit by general optical signal processing.
Accordingly, the present invention provides a polarization orthogonal multiplexed signal light regeneration apparatus and a polarization orthogonal multiplexed signal light regeneration method capable of obtaining good operation by optical signal processing even for polarization orthogonal multiplexed signals. With the goal.

  To achieve the above object, the present invention provides an optical signal separation means for separating a separated optical signal from an input polarization orthogonal multiplexed signal, a clock pulse extracting means for extracting a clock pulse from the separated optical signal, An optical signal regeneration means for obtaining an optical reproduction signal by synchronizing a polarization orthogonal multiplexed signal with a clock pulse extracted by the clock pulse extraction means, The clock pulse extracting means further comprises polarization control means for outputting the polarization orthogonal multiplexed signal in a polarization state in which orthogonal polarizations of the orthogonal multiplexed signal are fixed at a predetermined angle with the traveling direction as an axis. Is characterized in that a polarization orthogonal multiplexed signal outputted from the polarization control means is inputted.

  As described above, according to the polarization orthogonal multiplexing optical signal regenerator according to the present invention, at least an optical signal input to the clock pulse extraction unit is fixed at a predetermined angle with the traveling direction as an axis by the polarization control unit. By controlling the polarization state, fluctuations in the polarization state can be eliminated, so that at least the polarization dependence of the clock pulse extracting means is compensated and a good clock pulse can be extracted.

  In the polarization orthogonal multiplexed signal optical regenerator according to the present invention, the polarization control unit is configured such that orthogonal polarizations of the polarization orthogonal multiplexed signal are positioned in a horizontal direction and a vertical direction with respect to a traveling direction of the polarization orthogonal multiplexed signal. After adjusting the polarization orthogonal multiplexed signal to the polarization state to be rotated, the polarization orthogonal multiplexed signal is rotated about the traveling direction as an axis to obtain a polarization state of 45 ° / 135 ° with respect to the horizontal direction. Is preferred. In this way, the polarization state positioned in the horizontal direction and the vertical direction can be controlled from the other polarization states to the horizontal direction and the vertical method according to the present invention, and the optical signal adjusted to the linear polarization state is set in the horizontal direction. On the other hand, by setting the angle to 45 ° / 135 °, it is possible to input to the clock extracting means in an optimum polarization state.

  Also, in the polarization orthogonal multiplexing signal optical regenerator according to the present invention, the polarization control means outputs the separated optical signal separated by the optical signal separation means in a polarization state fixed at the predetermined angle. In this case, the output separated optical signal may be input to the clock pulse extracting means.

  Further, the polarization control means may output the polarization orthogonal multiplexed signal before being separated by the optical signal separation means in a polarization state fixed at the predetermined angle. A separated optical signal may be input to the optical signal separating means. With this configuration, since the polarization orthogonal multiplexed signal can be input to the optical signal regeneration means after controlling the polarization state, the polarization dependence is compensated for the optical signal light regeneration means as well. It is possible to secure a reliable optical signal light reproduction operation.

  Still further, the optical signal separating means may separate the separated optical signal from the optical signal processed by the optical signal regenerating means. In this case, the separated optical signal is converted from the separated optical signal to the clock pulse extracting means. May be input. Thus, since the clock pulse is extracted by feeding back the optical signal processed by the optical signal light reproducing means, a more accurate clock pulse can be obtained.

  Furthermore, the polarization orthogonal multiplexing signal optical regenerator according to the present invention may comprise an optical waveform shaping device that shapes the waveform of an optical signal before being input to the optical signal demultiplexing means, and outputs from the optical regenerating means. An optical waveform shaping device that shapes the waveform of the optical signal thus obtained may be further provided. The clock pulse extracting means is preferably processed by an electric signal.

  In order to achieve the above object, the present invention provides an optical signal separation step of separating an input polarization orthogonal multiplexed signal into a separated optical signal, and a clock pulse extraction step of extracting a clock pulse from the separated optical signal, An optical signal regeneration step of obtaining an optical reproduction signal by synchronizing the polarization orthogonal multiplexing signal with the clock pulse extracted by the clock pulse extraction means, A polarization control step of outputting the polarization orthogonal multiplexed signal in a polarization state in which the orthogonal polarization of the polarization orthogonal multiplexed signal is fixed at a predetermined angle with the traveling direction as an axis; In the extraction step, the polarization orthogonal multiplexed signal output from the polarization control step is input.

  In the polarization orthogonal multiplexed signal light regeneration method according to the present invention, the polarization control step may be configured such that the polarization control step is such that the orthogonal polarization of the polarization orthogonal multiplexed signal is in the traveling direction of the polarization orthogonal multiplexed signal. After the polarization orthogonal multiplex signal is adjusted to the polarization state positioned in the horizontal direction and the vertical direction, the polarization orthogonal multiplex signal is rotated about the traveling direction as an axis to be 45 ° / 135 ° with respect to the horizontal direction. Preferably, the polarization state is Further, the polarization control step may output the separated optical signal separated by the optical signal separation step in a polarization state fixed at the predetermined angle. The polarization orthogonal multiplexed signal before being separated by the optical signal separation step may be output in a polarization state fixed at the predetermined angle. Further, the optical signal separation step may separate the separated optical signal from the optical signal processed by the optical signal regeneration step.

  As described above, according to the present invention, it is possible to provide a polarization orthogonal multiplexed signal light regenerating apparatus capable of obtaining good operation even with a polarization orthogonal multiplexed signal.

  Next, a first embodiment of a polarization orthogonal multiplexing signal regenerator according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a polarization orthogonal multiplexed signal light reproducing apparatus according to the first embodiment. The polarization orthogonal multiplexed signal optical regenerator according to the first embodiment receives an optical signal and separates the separated optical signal from the optical signal and the separated optical signal from the optical signal separating unit 1. A polarization control unit 2 for controlling and outputting the polarization state, a clock pulse extraction unit 3 for inputting the separated optical signal controlled by the polarization control unit 2 and extracting a clock pulse from the separated optical signal, An optical signal light regeneration unit 4 for inputting an optical signal from the optical signal separation unit 1 on one side and a clock pulse from the clock pulse extraction unit 3 on the other side and outputting an optical signal reproduced in synchronization with the clock pulse. And.

  The optical signal separation unit 1 includes an optical coupler and the like, and is configured to separate an optical signal input from one side in a state of a polarization orthogonal multiplexed signal in accordance with an arbitrary ratio. Here, the polarization state of the optical signal input to the optical signal separation means 1 and the polarization state of the separated separated optical signal fluctuate by rotating around the traveling direction, for example, FIG. ), The polarization state of 0 ° / 90 ° positioned in the horizontal direction and the vertical direction of the orthogonal polarization signal is input in the polarization state rotated by x degrees.

  The polarization controller 2 includes a polarization controller 5 that adjusts the polarization state, a polarization beam splitter 6 that receives a part of the optical signal output from the polarization controller 5 and separates it into a vertical component and a horizontal component. The clock intensity of either the vertical component or the horizontal component is monitored, and a control value is output to the polarization controller 5 so that the clock intensity is maximized. As shown in FIG. A clock monitor 7 that dynamically controls the separated optical signal in a polarization state of 0 ° / 90 ° positioned in a horizontal direction and a vertical component with the traveling direction as an axis, and a 0 ° / 90 ° controlled by the clock monitor 7 The polarization in the polarization state is input and the polarization axis is rotated by 45 ° using a λ / 2 wave plate. As shown in FIG. 2C, each polarization is 45 ° with respect to the horizontal direction. Λ / to control rotation to a 45 ° / 135 ° polarization state of 135 ° A two-rotor 8. In the case of the 0 ° / 90 ° polarization state, the value of the monitor of the clock monitor 7 becomes the maximum value, so that the polarization state can be reliably controlled as compared with the state deviated from 0 ° / 90 °. At the same time, it can be output stably from the polarization beam splitter 6. Further, by adjusting the polarization state to 45 ° / 135 °, it is possible to input to the semiconductor mode-locked laser 11 described later in an optimum polarization state.

  The clock pulse extraction unit 3 attenuates the intensity of the input optical signal, and dynamically adjusts the optical variable attenuator 9 to dynamically adjust the optical input level to the semiconductor mode-locked laser to an optimum input level. And a circulator 10 that outputs an optical signal input from the first terminal to the second terminal and outputs an optical signal input from the second terminal to the third terminal, and is close to the frequency of the oscillation signal And a semiconductor mode-locked laser (MLLD) 11 using an injection locking phenomenon that outputs a clock pulse of the same frequency when an optical signal is injected.

  The optical signal light regeneration unit 4 includes an optical receiver 12 that converts an input optical signal into an electric signal, a clock amplifier 13 that amplifies only the clock frequency of the input electric signal, and a clock signal of the input electric signal. A clock band-pass filter (clock BPF) 14 that passes only the light, and an optical modulator 15 that outputs an optical signal input from one side with the phase, amplitude, etc. changed in accordance with the modulation signal input from the other. I have.

  In the polarization orthogonal multiplexing optical signal regenerator according to the first embodiment, an optical amplifier 16 for amplifying and outputting the input optical signal is installed at the entrance, and the regenerated optical signal is input to obtain the signal. An optical amplifier 18 that amplifies and outputs to the outside is installed immediately before the output end. Further, an optical delay line 17 is provided between the optical signal separation unit 1 and the optical modulator 15 for measuring and outputting a delay time by giving a delay time to the input optical signal. Here, the optical modulator 15 can be configured by an electroabsorption modulator or a LiNbO3 modulator.

  Next, the operation of the polarization orthogonal multiplexed signal regenerator according to the first embodiment will be described. When the polarization orthogonal multiplexed signal deteriorated and attenuated by transmission is input to the optical amplifier 16, the optical amplifier 16 amplifies it, and the optical signal separation unit 1 separates the separated optical signal from the polarization orthogonal multiplexed signal. . When the separated optical signal is input to the polarization controller 2, the clock monitor 7 dynamically controls the polarization controller 5 to change the separated optical signal to a state of 0 ° / 90 ° ((( After the adjustment to b)), the λ / 2 rotator 8 is controlled to control and output the separated optical signal to a polarization state of 45 ° / 135 ° ((c) in FIG. 2).

  The separated optical signal controlled to the polarization state of 45 ° / 135 ° is input to the clock pulse extraction unit 3, and the optical variable attenuator 9 adjusts the intensity so as to obtain a constant optical signal level, and then MLLD 11 To generate a clock pulse having the same period as the separated optical signal.

  Next, when the clock pulse extracted by the clock pulse extraction unit 3 is input to the optical signal regeneration unit 4, the optical receiver 12 converts the clock pulse, which is an optical signal, into an electrical signal, and then the clock amplifier 13 Amplifies the electric signal only in the vicinity of the clock pulse, and the clock BPF 14 performs waveform shaping by removing electric signal noise other than the clock pulse by filtering.

  Finally, the clock pulse generated in this way is input to one side as a modulation signal, and the polarization orthogonal multiplexed signal to which the output signal is delayed so that the output signal is most stable is input from the optical delay line 17. Then, the optical modulator 15 generates an optical signal by synchronizing the polarization orthogonal multiplexed signal with a clock pulse that is a modulation signal. Further, the amplifier 18 amplifies this optical signal and outputs a regenerated optical signal.

  As described above, according to the polarization orthogonal multiplexing signal reproducing apparatus according to the first embodiment, the polarization state is dynamically controlled to 0 ° / 90 ° by the polarization controller 5, and then the λ / 2 rotator 8 is used. It can be rotated to 45 ° / 135 ° and controlled to an optimum polarization state for input to the semiconductor mode-locked laser 11. The polarization state of light in the optical fiber always changes depending on the temperature of the external environment of the optical fiber, etc., but a control loop can be formed by the clock monitor 7 so that the optimum polarization state can always be controlled. Further, the process of extracting the clock in the clock pulse extraction unit 3 is all performed by optical signal processing, thereby realizing high-speed signal processing, and the step of waveform shaping using the clock amplifier 13 and the clock BPF 14 in the optical signal reproduction unit 4. By performing electrical signal processing, waveform shaping can be performed without performing complicated polarization control when NOLM or the like is used.

  Next, a second embodiment of the polarization orthogonal multiplexing signal regenerator according to the present invention will be described with reference to FIG. In the polarization orthogonal multiplexed signal optical regenerator according to the second embodiment, the optical signal separation unit 1, the polarization control unit 2, the clock pulse extraction unit 3 and the optical signal light reproduction unit 4 are as shown in FIG. After the input optical signal is adjusted to a polarization state of 45 ° / 135 ° by the polarization controller 2, the separated optical signal is separated by the optical signal separator 1. Here, the optical modulator 15 often has polarization dependence in which the state of the output signal depends on the polarization state of the input optical signal. The polarization state of the signal in the optical modulator 15 can be compensated by inputting it to the optical modulator 15 after controlling the polarization state by.

  Furthermore, a third embodiment of the polarization orthogonal multiplexing signal regenerator according to the present invention will be described with reference to FIG. In the polarization orthogonal multiplexed signal optical regenerator according to the third embodiment, the optical signal demultiplexer 1, the polarization controller 2, the clock pulse extractor 3 and the optical signal regenerator 4 are arranged as shown in FIG. The polarization orthogonal multiplexed signal controlled to the 45 ° / 135 ° polarization state by the wave control unit 2 is input to the optical signal regeneration unit 4, and the polarization orthogonal multiplexed signal output from the optical signal regeneration unit 4 is the optical signal. The optical signal regeneration unit 4 is separated by the separation unit 1 and input to the clock pulse extraction unit 3, and the optical signal regeneration unit 4 is arranged to perform optical regeneration in synchronization with the clock pulse extracted by the clock pulse extraction unit 3. In such a polarization orthogonal multiplexing signal regenerator according to the third embodiment, the polarization control unit 2 adjusts the input polarization orthogonal multiplexed signal to a 45 ° / 135 ° polarization state to generate an optical signal. The light is output to the modulator 15, and the optical modulator 15 generates a reproduction optical signal by synchronizing the input optical signal with a clock pulse that is a modulation signal. The clock pulse is a signal generated by inputting a part of the reproduction optical signal output from the optical modulator 15 to the optical delay line 17 or the clock pulse extraction unit 3. In this way, since the clock pulse is extracted by feeding back the optical signal whose waveform has been shaped by the optical signal reproducing unit 4, a clock pulse with better characteristics can be obtained.

  Also, as shown in FIGS. 5 to 8, by installing the optical waveform shaping device 19 before and after the optical signal regeneration process, the function as an entire optical 3R regeneration function can be improved, and optical regeneration with better characteristics. Can be realized.

1 is a block diagram of a polarization orthogonal multiplexed signal light reproducing apparatus according to a first embodiment of the present invention. FIG. It is a perspective view of a polarization showing a polarization state in a polarization orthogonal multiplexed signal light reproducing apparatus, and a diagram showing a declination. It is a block diagram of a polarization orthogonal multiplexed signal light reproducing apparatus according to a second embodiment. It is a block diagram of a polarization orthogonal multiplexing signal light reproducing apparatus according to a third embodiment. It is a block diagram of a polarization orthogonal multiplexing signal light reproducing apparatus according to another embodiment. It is a block diagram of a polarization orthogonal multiplexing signal light reproducing apparatus according to another embodiment. It is a block diagram of a polarization orthogonal multiplexing signal light reproducing apparatus according to another embodiment. It is a block diagram of a polarization orthogonal multiplexing signal light reproducing apparatus according to another embodiment. It is a block diagram of the optical reproduction apparatus which concerns on the conventional Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical signal separation part, 2 ... Polarization control part, 3 ... Clock pulse extraction part, 4 ... Optical signal reproduction | regeneration part, 5 ... Polarization controller, 6 ... Polarization beam splitter, 7 ... Clock monitor, 8 ... λ / 2 rotators, 9 ... variable optical attenuator, 10 ... circulator, 11 ... MLLD, 12 ... optical receiver, 13 ... clock amplifier, 14 ... clock BPF, 15 ... optical modulator, 16, 18 ... optical amplifier, 17 ... Optical delay line, 19 ... optical waveform shaping device.

Claims (8)

An optical signal separating means for separating the separated optical signal from the input polarization orthogonal multiplexed signal;
Clock pulse extracting means for extracting a clock pulse from the separated optical signal;
An optical modulator that generates an optical signal in synchronization with the clock pulse extracted by the clock pulse extraction unit, and amplifies the optical signal generated by the optical modulator to generate an optical reproduction signal A polarization orthogonal multiplexed signal light regenerating device comprising:
A polarization control means for outputting the polarization orthogonal multiplex signal in a polarization state in which the orthogonal polarization of the polarization orthogonal multiplex signal is fixed at a predetermined angle with the traveling direction as an axis;
The clock pulse extraction means has a semiconductor mode-locked laser using an injection locking phenomenon, and when the polarization orthogonal multiplexed signal output from the polarization control means is input , the separated optical signal and Generate clock pulses with the same period,
The polarization orthogonal multiplexing signal light reproducing apparatus characterized in that the polarization control means outputs the separated optical signal separated by the optical signal separation means in a polarization state fixed at the predetermined angle . An optical modulator that generates an optical signal by synchronizing an input polarization orthogonal multiplexed signal with a clock pulse, and amplifies the optical signal generated by the optical modulator to obtain an optical reproduction signal; ,
An optical signal separating means for separating a separate optical signal from the polarization orthogonal multiplex signal is an optical signal processed by the optical signal regeneration means,
A clock pulse extraction means for extracting the clock pulse from the separated optical signal and inputting the clock pulse to the optical signal regeneration means, and a polarization orthogonal multiplexed signal light regeneration apparatus comprising:
A polarization control means for outputting the polarization orthogonal multiplex signal in a polarization state in which the orthogonal polarization of the polarization orthogonal multiplex signal is fixed at a predetermined angle with the traveling direction as an axis;
The clock pulse extraction means has a semiconductor mode-locked laser using an injection locking phenomenon, and when the polarization orthogonal multiplexed signal is input, generates a clock pulse having the same period as the separated optical signal,
It said polarization control means, said optical signal separating means polarization orthogonal multiplex signal light reproducing apparatus you and outputting in polarization states separating optical signals separated fixed at the predetermined angle by. The polarization control unit adjusts the polarization orthogonal multiplex signal to a polarization state in which orthogonal polarizations of the polarization orthogonal multiplex signal are positioned in a horizontal direction and a vertical direction with respect to a traveling direction of the polarization orthogonal multiplex signal. 3. Polarization orthogonality according to claim 1 or 2 , characterized in that the polarization orthogonal multiplexing signal is rotated around the traveling direction as an axis to obtain a polarization state of 45 ° / 135 ° with respect to the horizontal direction. Multiple signal light regenerator. Polarization orthogonal multiplex signal light reproducing device according to any one of claims 1 to 3, characterized in that it comprises an optical waveform shaping device for performing waveform shaping of the optical signal before being input to the optical signal separating means. Polarization orthogonal multiplex signal light reproducing device according to any one of claims 1 to 4, further comprising a optical waveform shaping device for performing waveform shaping of the optical signal output from said optical reproducing means. An optical signal separation step of separating the input polarization orthogonal multiplexed signal into a separated optical signal;
A clock pulse extracting step of extracting a clock pulse from the separated optical signal;
An optical modulator that generates an optical signal by synchronizing the polarization orthogonal multiplexed signal with the clock pulse extracted by the clock pulse extracting means , amplifies the optical signal generated by the optical modulator , An optical signal regeneration step, and a polarization orthogonal multiplexed signal light regeneration method comprising:
A polarization control step of outputting the polarization orthogonal multiplex signal in a polarization state in which the orthogonal polarization of the polarization orthogonal multiplex signal is fixed at a predetermined angle with the traveling direction as an axis;
In the clock pulse extraction step, injection locking phenomenon semiconductor mode-locked laser using the is used, the polarization orthogonal multiplex signal after being output by the polarization control step is input, the separation optical signal and Generate clock pulses with the same period,
The polarization orthogonal multiplexed signal light reproduction characterized in that, in the polarization control step, the separated optical signal separated in the optical signal separation step is output in a polarization state fixed at the predetermined angle. Method. Using an optical modulator that generates an optical signal by synchronizing the input polarization orthogonal multiplexed signal with a clock pulse, and amplifying the optical signal generated by the optical modulator to obtain an optical reproduction signal; and
An optical signal separation step for separating the separated light signals from the polarization orthogonal multiplex signal is an optical signal processed by the optical signal regeneration step,
A clock pulse extraction step for extracting the clock pulse from the separated optical signal, and a polarization orthogonal multiplexed signal light regeneration method comprising:
A polarization control step of outputting the polarization orthogonal multiplex signal in a polarization state in which the orthogonal polarization of the polarization orthogonal multiplex signal is fixed at a predetermined angle with the traveling direction as an axis;
In the clock pulse extraction step, a semiconductor mode-locked laser using an injection locking phenomenon is used, and when the polarization orthogonal multiplexed signal is input, a clock pulse having the same period as the separated optical signal is generated,
The polarization in the control step, the optical signal separating polarization orthogonal multiplex signal light reproducing how to and outputting in polarization states separating optical signals separated fixed at the predetermined angle by step. In the polarization control step , the polarization orthogonal multiplex signal is adjusted to a polarization state in which the orthogonal polarization of the polarization orthogonal multiplex signal is positioned in a horizontal direction and a vertical direction with respect to a traveling direction of the polarization orthogonal multiplex signal. The polarized wave according to claim 6 or 7 , wherein the polarization orthogonal multiplexed signal is rotated about the traveling direction as an axis to obtain a polarization state of 45 ° / 135 ° with respect to the horizontal direction. Orthogonal multiplexed signal optical regeneration method.

Images