JP5367316B2 - Optical regenerator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately reproduce signal light, without enlarging a circuit scale. <P>SOLUTION: A PBS (polarization beam splitter) 16 of an optical loop regenerating circuit 20 outputs a first polarization component and a second polarization component which is orthogonal to the first polarization component, from the composited light of the signal light and pump light to two output ports. A generation circuit 18 is provided on a light-generating loop which connects the two output ports to each other in a loop form. The generation circuit 18 parametrically amplifies the first polarization component and the second polarization component. The composited light which propagates the inside of the light-generating loop, is remultiplexed in the PBS 16 and output from the input port of the PBS 16, passes a BPF 19 allowing the passage of the light of a wavelength &lambda;s of the signal light, and the reproduced signal light is output from the BPF 19. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an optical regenerator for polarization multiplexed optical signals.

In order to realize high frequency utilization efficiency and ultra high-speed large-capacity transmission, research on polarization multiplexing transmission is underway. In polarization multiplexing transmission, information is placed on two polarizations whose directions are 90 degrees different (for example, horizontal and vertical) in the vertical direction of the traveling direction. As a result, compared to conventional transmission using a single polarization,
Two times the amount of information can be transmitted. That is, when the same amount of information is sent, transmission can be performed at a transmission rate (symbol rate) that is half that of transmission using a conventional single-directional polarization.

  However, polarization multiplexed transmission is easily affected by polarization crosstalk in the polarization multiplexing / demultiplexing section and polarization crosstalk due to the influence of polarization mode dispersion (PMD). For this reason, the transmission characteristics deteriorate, and the transmission distance and the number of wavelengths are limited. Therefore, it is necessary to arrange an optical regenerator that reproduces an optical signal on the transmission line.

  In the signal reproduction technique, signal reproduction has been realized conventionally using electric signal processing. However, it is expected that the problems of electric signal processing can be solved by using optical signal processing from the viewpoint of the limitation of the processing speed of electric signal processing and the increase in power consumption. In optical signal processing, there is a response speed of femtoseconds or more depending on a device such as an optical fiber. Therefore, even if the transmission speed is further increased, a sufficient response speed is expected.

For signal playback, 2R playback (reamplifying, reshaping) and 3R playback (reamplifying, reshaping)
reshaping, retiming). Up to now, many studies have been made on application of optical regenerators in transmission using only polarization in a single direction.

  It is impossible to directly apply an optical regenerator for polarization in a single direction to a polarization multiplexed signal. If it is applied as it is, the polarization multiplexed signal is once separated and optical regeneration is applied to each polarization.

  For a signal having a single polarization direction and an arbitrary polarization state, for example, Patent Document 1 includes an optical circulator, a polarization beam splitter (PBS), and a saturable absorber, and the polarization beam splitter and the saturable absorber. Has proposed a device that realizes optical regeneration in order to form a loop and pass light from the beam splitter through the loop. In this apparatus, an attempt is made to realize optical regeneration that does not depend on the polarization state of incident light.

  The optical regeneration method disclosed in Patent Document 1 is also referred to as a polarization diversity method. When light in an arbitrary polarization state is incident on PBS, it is separated into an X polarization component and a Y polarization component, Each polarization component is optically regenerated and combined again. For optical regeneration, a saturable absorption device is used. The saturable absorption device has a characteristic that the loss is large when the optical input power is low, and the loss is low when the optical input power is high, and noise on the space (0) side of the intensity modulation signal can be reduced.

However, when the polarization diversity method disclosed in Patent Document 1 is applied to a polarization multiplexed signal as it is, it does not work effectively. That is, when polarization separation occurs when the polarization state of the signal is incident without being aligned with the polarization axis of the PBS, the X polarization component and the Y polarization component of the polarization multiplexed signal are output to the same PBS output port, This causes signal degradation.
JP 2007-316189 A “Optical level equalization based on gainment in fiber optical parametric amplifier” Inoue, Electronics Letters, Vol. 36, no. Issued in June 2000 “3R Regeneration of a 40-Gbit / s Optical Signal by Optical Parametric Amplification in a High-Nonlinear Fiber” Published by Yu et al., OFC 2005, OtuO1, March 2005

  In general, it is impossible to directly apply an optical regenerator for polarization in a single direction to a polarization multiplexed signal. If it is applied as it is, two similar optical regeneration circuits are provided, the polarization multiplexed signal is once separated, one optical regeneration circuit is used for one polarization, and the other polarization is used. Needs to use the other optical regeneration circuit.

As one of the optical regeneration methods, there is an optical regeneration method using parametric amplification. This method uses a parametric process in which an optical fiber becomes a nonlinear medium. From two photons of the input signal (pump light), one photon is generated at each of two wavelengths having a phase matching condition. In particular, when signal light having a wavelength that satisfies a phase matching condition is incident along with pump light, the signal light is amplified by a parametric process (parametric amplification).
. This amplification characteristic has a characteristic of being saturated when the incident power of signal light is increased. This saturation characteristic provides a limit effect.

  Non-Patent Document 1 and Non-Patent Document 2 disclose that optical 2R regeneration and optical 3R regeneration are performed using the limit effect of the parametric amplification.

  However, even in the optical regeneration using the parametric amplification, the above-mentioned problem, that is, two optical regeneration circuits are provided, the polarization multiplexed signal is once separated, and one optical regeneration circuit is provided for one polarization. The problem remains that the other optical regeneration circuit must be used for the other polarization.

  An object of the present invention is to provide an optical reproducing apparatus capable of appropriately reproducing signal light without increasing the circuit scale.

An object of the present invention is to accept signal light of a polarization orthogonal multiplexed signal in which two optical signals of orthogonal polarization states propagated through a transmission line by polarization multiplexing transmission are multiplexed and regenerate the signal light. An optical regenerator that outputs
Pump light generating means for generating pump light having a wavelength λp different from the wavelength λs of the signal light;
First polarization control means for controlling the polarization state of the signal light;
Second polarization control means for controlling the polarization state of the pump light;
Multiplexing means for multiplexing the signal light output from the first polarization control means and the pump light output from the second polarization control means;
The combined light from the multiplexing means is received at the input port, and the first polarized wave component and the second polarized wave component orthogonal to the first polarized wave component are output from the combined light into two outputs. A polarization beam splitter that outputs to a port, an optical regeneration loop that is a transmission path in which the two output ports are connected in a loop, and the first polarization component and the second An optical regeneration loop means having a reproducing means for parametrically amplifying the polarization component of
Propagating through the light regeneration loop of the light regeneration loop means, recombined in the polarization beam splitter, and received the regenerated combined light output from the input port of the polarization beam splitter, Bandpass filter means for passing light of wavelength λs;
At least three ports are connected to each of the multiplexing means, the optical regeneration loop means, and the band pass filter means, and the combined light from the multiplexing means is output to the optical regeneration loop means And an optical path determining means for outputting the regenerated combined light from the optical regeneration loop means to the band pass filter means.

In a preferred embodiment, the first polarization control means has a polarization state of the signal light, and the first polarization component of the polarization orthogonal multiplexed signal is a first axis in the polarization beam splitter. And control to be linearly polarized,
The second polarization control means is configured to change a polarization state of the pump light with respect to the first axis in the polarization beam splitter when combined light including the pump light is input to the polarization beam splitter. In order to obtain a linearly polarized light of 45 degrees.

  In a preferred embodiment, the optical regeneration loop means includes polarization adjustment means that is disposed on the optical regeneration loop and adjusts the polarization states of the first polarization component and the second polarization component. .

In a more preferred embodiment, the polarization beam splitter maintains the polarization state of the input combined light, and the first polarization component and the second polarization component are transmitted from the two output ports. Configured to output,
The jumper cable constituting the optical regeneration loop, and the regeneration means are configured to maintain the polarization state; and
The polarization adjusting unit is configured to rotate the polarization states of the received first polarization component and second polarization component by 90 °.

In another preferred embodiment, the first polarization component is output from the first output port of the polarization beam splitter and propagates on the optical regeneration loop, and the second port of the polarization beam splitter. Is again input to the polarization beam splitter, the second polarization component is output from the second output port, propagates on the optical reproduction loop, and is again input to the polarization beam at the first port of the polarization beam splitter. Input to the splitter,
The polarization adjusting means is
When the first polarization component is input to the polarization beam splitter again at the second port, the second polarization component when the polarization state is output from the second port And the same polarization state, and
When the second polarization component is input to the polarization beam splitter again at the first port, the first polarization component when the polarization state is output from the first port The polarization states of the first polarization component and the second polarization component are controlled so as to be the same as the polarization state.

In still another preferred embodiment, the polarizing beam splitter is configured to rotate and output only the polarization state of any one of the polarization components, and
The jumper cable that constitutes the optical regeneration loop and the regeneration means are configured to maintain polarization.

In a preferred embodiment, signal light polarization control means for generating a first control signal for the first polarization control means,
First demultiplexing means disposed between the first polarization control means and the multiplexing means;
A first polarization state observation unit that receives the signal light demultiplexed by the first demultiplexing unit and calculates an index value based on a polarization state of the signal light; and the first polarization state observation Signal light control signal generating means for generating a first control signal for controlling the first polarization control means based on the index value calculated by the means so as to optimize the index value. With signal light polarization control means,
From the output port of the first polarization control means to the input port of the polarization beam splitter of the optical regeneration loop means via the first demultiplexing means, the multiplexing means, and the optical path determining means Are configured to maintain their polarizations.

In another preferred embodiment, signal light polarization control means for generating a first control signal for the first polarization control means,
In the light regeneration loop means, first demultiplexing means disposed on the light regeneration loop from one output port of the polarization beam splitter;
A first polarization state observation unit that receives the signal light demultiplexed by the first demultiplexing unit and calculates an index value based on a polarization state of the signal light; and the first polarization state observation Signal light control signal generating means for generating a first control signal for controlling the first polarization control means based on the index value calculated by the means so as to optimize the index value. Signal light polarization control means is provided.

Further, in a preferred embodiment, the pump light polarization control means for generating a second control signal for the second polarization control means,
Second demultiplexing means disposed on the optical transmission line from the output port of the bandpass filter means;
A polarization acquisition unit that receives the regenerated signal light demultiplexed by the second demultiplexing unit and acquires respective polarization components of the signal light; and a polarization acquired by the polarization acquisition unit. Second polarization state observation means for calculating an index value based on the light intensity of each of the wave components, and the second polarization state observation means so that the index value calculated by the second polarization state observation means is optimal. A pump light polarization control means having a pump light control signal generation means for generating a second control signal for controlling the polarization control means of
Optical path from the input port of the polarization beam splitter of the optical regeneration loop means to the polarization acquisition means via the optical path determination means, the band pass filter means, and the second demultiplexing means Is configured to retain its polarization.

In another preferred embodiment, pump light polarization control means for generating a second control signal for the second polarization control means,
A second demultiplexing means and a third demultiplexing means respectively disposed on the optical regeneration loop from the two output ports of the polarization beam splitter of the optical regeneration loop;
Second polarization state observing means for calculating an index value based on the light intensity of each polarization component demultiplexed by the second demultiplexing means and the third demultiplexing means; and the second polarization A pump light control signal generating means for generating a second control signal for controlling the second polarization control means so that the index value calculated by the wave state observing means is optimized. Wave control means is provided.

  In a preferred embodiment, the pump light generating means generates continuous light having the wavelength λp.

  In another preferred embodiment, the pump light generating means receives the signal light and generates pump light that is clock light synchronized with data modulation of the signal light.

  ADVANTAGE OF THE INVENTION According to this invention, the optical reproducing apparatus which can reproduce | regenerate signal light appropriately, without enlarging a circuit scale can be provided.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing the configuration of the optical regenerator according to the first embodiment of the present invention. The optical regenerator 10 is arranged in the transmission path of the polarization multiplexing transmission system, and can regenerate and output an optical signal with deteriorated transmission quality. As shown in FIG. 1, an optical regenerator 10 according to this embodiment includes a polarization controller 11 that controls the polarization state of signal light input from a transmission line, and pump light that generates pump light of a predetermined wavelength. Receiving the combined light from the generation circuit 12, the polarization controller 13 for controlling the polarization state of the pump light output from the pump light generation circuit 12, the optical coupler 14 for combining the signal light and the pump light, and the optical coupler 14. The combined light is output to an optical regeneration loop circuit 20 described later, and an optical signal from the optical regeneration loop circuit is received, and the received optical signal is sent to a band pass filter (BPF) 19 disposed on the output side. And an optical circulator 15 for outputting. Further, the optical regenerator 10 according to the present embodiment has an optical regenerative loop circuit 20 for receiving the combined light from the optical circulator 15 and regenerating the signal light included in the combined light.

  The optical regeneration loop circuit 20 includes a polarization beam splitter (PBS) 16, a polarization adjustment circuit 17, and a regeneration circuit 18.

  Schematically, the optical regenerator 10 according to the present embodiment operates as follows. In the present embodiment, a polarization orthogonal multiplexed signal obtained by multiplexing two optical signals having orthogonal polarization states in the transmission path is propagated as signal light and accepted by the optical regenerator 10.

  The polarization state (SOP: State of Polarization) of the signal light is a straight line on the same axis as the X axis of the PBS 16 in which either the X polarization or Y polarization, which is a component of the polarization orthogonal multiplexed signal, is the same. The polarization controller 11 adjusts the polarization so as to be polarized. The polarization controller 11 includes, for example, one or more λ / 2 plates and one or more λ / 4 plates. The λ / 2 plate and the λ / 4 plate can be rotated around the optical axis by the control signal, respectively, and the polarization directions of the X-polarization component and the Y-polarization component of the polarization orthogonal multiplexed signal can be adjusted simultaneously. . The same applies to the polarization controller 13. The control of the polarization state using the polarization controllers 11 and 13 will be described in detail later.

  The pump light generation circuit 12 generates pump light that is continuous light (CW light) having a wavelength λp different from the wavelength λs of the signal light. The polarization controller 13 adjusts the polarization state (SOP) of the pump light so that the light intensity from each of the output ports of the PBS 16 becomes equal. Ideally, the pump light is 45-degree linearly polarized light with respect to the X axis of the PBS 16. The signal light output from the polarization controller 11 and the pump light output from the polarization controller 13 are combined by the optical coupler 14.

  The optical circulator 15 outputs light received from each port from one adjacent port. The optical circulator 15 shown in FIG. 1 outputs input light from a port adjacent in the clockwise direction in FIG. For example, the combined light output from the optical coupler 14 passes through the optical circulator 15 and enters the PBS 16. Further, the light output from the PBS 16 is incident on the BPF 19 through the optical circulator 15.

In the combined light incident on the PBS 16 of the optical regeneration loop circuit 20, the signal light S (λs) is demultiplexed into an X polarization component S ₁ (λs) and a Y polarization component S ₂ (λs). Further, since the pump light S (λp) is ideally linearly polarized at 45 degrees with respect to the X axis of the PBS 16, signals having the same light intensity are output from the two output ports of the PBS 16. . At the output port of the PBS 16, the polarization states of the X-polarized light and the Y-polarized signal light and the pump light are linearly polarized light in the same direction. 2A is a diagram illustrating an example of the wavelength λs of the signal light and the wavelength λp of the pump light, and FIG. 2B is a diagram illustrating the polarization state of the signal light and the pump light at the input port 101 of the PBS 16. FIGS. 2C and 2D are diagrams showing the polarization states of the signal light and the pump light at the output ports 102 and 103 of the PBS 16, respectively.

As shown in FIG. 2B, at the input port 101 of the PBS 16, the X polarization component S ₁ (λs) and the Y polarization component S ₂ (λs) of the signal light and the axis of the PBS 16 are 45. The pump light S (λp) that is linearly polarized light appears. At the output port 103 after passing through the PBS16 is, Y polarization component of the signal light _{S 2} ([lambda] s) and the Y polarization component of the pump light _{S 2 (λp)} appears. Meanwhile, at the output port 102, X polarization component of the signal light _{S 1} X polarization component of the ([lambda] s) and the pump light _{S 1 (λp)} appears. The signal passing through the PBS 16 will be described in more detail with reference to FIG.

  In the optical regeneration loop circuit 20, the light (see FIG. 2C) output from the PBS 16 to the port 102 is propagated clockwise through the transmission path (optical regeneration loop) on the loop and output from the PBS 16 to the port 103. The light (see FIG. 2D) is propagated in the light regeneration loop counterclockwise. The light propagated through the clockwise light regeneration loop and the counterclockwise light regeneration loop is subjected to light regeneration by the regeneration circuit 18, respectively. In the present embodiment, optical regeneration using parametric amplification is performed.

  Parametric amplification uses a parametric process in which an optical fiber becomes a nonlinear medium. From two photons of the input signal (pump light), one photon is generated at each of two wavelengths having a phase matching condition. In particular, when signal light having a wavelength satisfying the phase matching condition is incident together with the pump light, the signal light is amplified by a parametric process (parametric amplification). This amplification characteristic has a characteristic of being saturated when the incident power of signal light is increased. The limit effect can be obtained from this saturation characteristic. In the present embodiment, a high non-linear fiber (HNLF) is used as the regeneration circuit 18 in order to realize the parametric amplification.

  The optically regenerated X-polarized light and Y-polarized light are combined again in the PBS 16. In this embodiment, the polarization adjustment circuit 17 is arranged on the optical regeneration loop of the optical regeneration loop circuit, and the polarization of the light propagated through the clockwise optical regeneration loop and the counterclockwise optical regeneration loop is changed. Wave condition is adjusted. The function of the polarization adjustment circuit 17 will also be described later.

  The light combined in the PBS 16 enters the BPF 19 through the optical circulator 15. The BPF 19 is configured to pass light having a wavelength λs. Accordingly, only the signal light passes through the BPF 19, and finally the signal light that has been optically regenerated is output. The optically regenerated signal light output from the BPF 19 is sent to the transmission path.

  Hereinafter, the optical regeneration loop circuit 20 according to the present embodiment will be described. At each port of the PBS 16, the direction of polarization of the input / output signal is defined. For this reason, the input signal needs to be incident in the prescribed polarization direction, and the output signal is output in the prescribed polarization direction.

For example, the following two modes are conceivable as the polarization state of the output port of the 1-port input 2-port PBS.
(1) 0 ° (horizontal) and 90 ° (vertical) of the input signal of the polarization orthogonal multiplexed signal are output as polarization states of 0 ° and 90 ° at the two output ports.
(2) 0 ° and 90 ° of the input / output signal of the polarization orthogonal multiplexed signal are output as a polarization state in which both of the two output ports are 0 ° or 90 °. That is, one component is rotated by 90 ° and output.

  In the present embodiment, the PBS 16 of the aspect (1) is used. In FIG. 3, at the input port, the signal light includes 0 ° polarization (X polarization) indicated by a solid line and 90 ° polarization (Y polarization) indicated by a broken line (see reference numeral 300). Then, 90 ° polarization (Y polarization) propagating in the light regeneration loop counterclockwise (see reference numerals 301 and 302) and 0 ° polarization (X polarization) propagating in the light regeneration loop clockwise. ) (See reference numerals 303 and 304).

  A case where the polarization state of propagating light (X-polarized light and Y-polarized light) is maintained in the jumper cable constituting the optical regeneration loop of the optical regeneration loop circuit 20 and in the regeneration circuit 18. Think. For example, this is a case where the jumper cable and the highly nonlinear fiber (HNLF) constituting the regenerative circuit 18 are configured by polarization maintaining fibers (PMF). The polarization adjustment circuit 17 causes the polarization adjustment circuit 17 to rotate the polarization state of the light propagating clockwise through the light regeneration loop and the light propagating counterclockwise by 90 °. Thus, each can be input again to the PBS 16 and combined. That is, in this case, the polarization adjustment circuit 17 may rotate the polarization state of each light by 90 °. A λ / 2 plate can be used as the polarization adjustment circuit 17. Alternatively, a polarization controller provided with at least one λ / 2 plate and λ / 4 plate may be applied as the polarization adjustment circuit 17.

  Alternatively, by using an adapter as the polarization adjustment circuit 17 instead of the wave plate, and adjusting the key of the adapter so that the fiber axis rotates 90 ° at the connection point of the adapter, the offset of 0 ° and 90 ° is obtained. It is also possible to switch the wave state.

  The polarization adjusting circuit 17 rotates the light in the polarization state of 0 ° (see reference numeral 303) clockwise through the light regeneration loop by 90 ° (see reference numeral 305), and rotates the light regeneration loop counterclockwise. The propagating light in the 90 ° polarization state (see reference numeral 301) is also rotated by 90 ° (see reference numeral 306).

  Further, when the jumper cable and the regeneration circuit 18 constituting the optical regeneration loop are not composed of PMF, as shown in FIG. 4, the light in the polarization state of 0 ° propagating clockwise through the optical regeneration loop is used. (See reference numeral 303) and 90 ° polarization state light (see reference numeral 301) propagating counterclockwise in the optical regeneration loop are both in an arbitrary polarization state (see reference numerals 402 and 401). Therefore, in this case, a polarization controller provided with at least one λ / 2 plate and one λ / 4 plate is applied as the polarization adjustment circuit 17 so that the λ / 2 plate and the λ / 4 plate are predetermined. The polarization state is appropriately controlled by rotating the angle. That is, the polarization adjustment circuit 17 adjusts the polarization so that the polarization direction at the port of the PBS 16 is appropriate in consideration of the change in polarization in the jumper cable or the like.

  Next, the generation of the control signal for the polarization controller 11 and the polarization controller 11 for controlling the polarization state of the signal light according to the present embodiment will be described. For the signal light, the X polarization component of the polarization orthogonal multiplexed signal is linear with respect to the X axis of the PBS 16 in order to appropriately perform polarization separation of the polarization orthogonal multiplexed signal in the PBS 16 of the optical regeneration loop circuit 20. It is necessary to control the polarization state so as to be polarized. Similarly, it is necessary to make the Y polarization component linearly polarized with respect to the Y axis of the PBS 16. In particular, for signal light that has propagated through the transmission line, the state of the transmission line always changes, and the polarization state of the incident polarization orthogonal multiplexed signal changes, so the polarization state must always be controlled. .

  FIG. 5 is a block diagram including a signal light polarization control unit that generates a control signal to the polarization controller 11 of the signal light according to the present embodiment. As shown in FIG. 5, the signal light polarization control unit 30 according to the present embodiment is output from the optical coupler 31 disposed on the transmission path between the polarization controller 11 and the optical coupler 14 and the optical coupler. And a polarization state observation unit 33 and a control signal generation unit 34.

  In the present embodiment, in order to control the polarization of the signal light incident on the PBS 16, an optical coupler 31 is provided in front (upstream side) of the optical coupler 14 for multiplexing with the pump light. The light is monitored. Therefore, the polarization state of the signal light needs to be constant from the output port of the polarization controller 11 to the input port of the PBS 16 of the optical regeneration loop circuit 20 in the downstream direction (see reference numeral 500). Therefore, in the present embodiment, the transmission path 500 from the output port of the polarization controller 11 to the input port of the PBS 16 of the optical regenerative loop circuit 20 is configured by a polarization maintaining fiber (PMF).

  The operation of the signal light polarization controller 30 shown in FIG. 5 will be described below. The signal light is branched by the optical coupler 31 and input to the polarizer 32. PBS may be used instead of the polarizer 32. The axis of the polarizer 32 (the axis of the PBS when PBS is used) is the same as the axis of the PBS 16 of the optical regeneration loop circuit 20. Therefore, if the polarization state is appropriately controlled in the polarizer 32, an appropriate polarization state can be obtained also at the input port of the PBS 16 of the optical regeneration loop circuit 20.

  The output of the polarizer 32 is sent to the polarization state observation unit 33, and a control signal for the polarization controller 11 is generated and output by the polarization state observation unit 33 and the control signal generation unit 34.

  For example, the polarization state observation unit 33 and the control signal generation unit 34 operate as follows.

  If the X polarization component and the Y polarization component of the orthogonal polarization signal to be separated by the PBS 16 are not properly separated by the PBS 16, the X polarization component and the Y polarization component are simultaneously output to one port. The A beat signal is observed when light including the X polarization component and the Y polarization component as described above is received by the optical receiver. When the beat signal is generated, the electric signal power is increased as compared with the case where the beat signal is not generated. Therefore, the polarization control state observation unit 33 includes an optical receiver and a power observation unit, and outputs a signal indicating the power state to the control signal generation unit 34. The control signal generation unit 34 receives a signal indicating the power state and outputs a control signal to the polarization controller 11 so that the power decreases (interference detection method). The polarization controller 11 rotates the angles of the λ / 2 plate and the λ / 4 plate according to the control signal.

  Alternatively, the polarization state observation unit 33 and the control signal generation unit 34 may have the following configuration. For example, in the transmitter, low-frequency intensity modulation is performed on one of the X-polarized wave and the Y-polarized wave of the polarization orthogonal signal that is a transmission signal, or low-frequency signals having different frequencies are applied to both the X-polarized wave and the Y-polarized wave The intensity modulation is performed, and the polarization state observation unit 33 monitors the low frequency signal.

  More specifically, the polarization state observation unit 33 uses an optical receiver to convert an X-polarized wave or a Y-polarized wave as an electric signal and a center frequency as a low-frequency modulation frequency. And only the low frequency signal is extracted. Next, the electric power is observed using an electric power meter or the like. The control signal generation unit 34 outputs a control signal to the polarization controller 11 so that the power is optimal (maximum or minimum).

  Next, generation of a control signal for the polarization controller 13 and the polarization controller 13 for controlling the polarization state of the pump light according to the present embodiment will be described.

  The polarization state of the pump light combined with the signal light in the optical coupler 14 and incident on the PBS 16 needs to be dynamically controlled according to the fluctuation state of the polarization. For the pump light, the polarization controller 13 adjusts the polarization state so that two signals having the same light intensity are output from the two output ports of the PBS 16. The pump light is ideally linearly polarized light that is 45 degrees with respect to the axis of the PBS 16 when incident on the PBS 16.

  As for the pump light, in the situation where the physical distance between the pump light generation circuit 12 and the PBS 16 is short, the jumper cable between them is fixed, and the polarization state of the pump light input to the PBS 16 hardly changes. Therefore, it is sufficient to adjust the polarization state once, and dynamic control is not necessary. However, in an environment where the jumper cable length is long and the polarization state of the pump light input to the PBS 16 changes, dynamic control is required. In this embodiment, the polarization state is dynamically controlled.

  FIG. 6 is a block diagram including a pump light polarization controller that generates a control signal to the polarization controller 13 of the signal light according to the present embodiment. As shown in FIG. 6, the pump light polarization control unit 40 according to the present embodiment outputs an optical coupler 41 that demultiplexes the output of the BPF 19 that outputs the optically regenerated signal light, and is output from the optical coupler 41. A PBS 42 that separates light, a polarization state observation unit 43, and a control signal generation unit 44 are provided. In FIG. 5 described above, only the signal light polarization controller 30 that generates the control signal to the polarization controller 11 is described. In FIG. 6, the pump that generates the control signal to the polarization controller 13 is described. Only the optical polarization controller 40 is described. Actually, the optical regenerator 10 includes both the signal light polarization controller 30 and the pump light polarization controller 40. 5 and 6 illustrate one of them for convenience of explanation.

  The pump light polarization controller 40 observes the light intensities of the X polarization component and the Y polarization component of the optically regenerated polarization orthogonal multiplexed signal. In this embodiment, since parametric amplification is used for light regeneration, both the X polarization component and the Y polarization component are amplified, but pump light is output with the same light intensity at the two output ports of the PBS 16. If not, this amplification is not performed evenly. Therefore, in the optical coupler 41 which is a monitor location, the light intensity of the X polarization component and the Y polarization component is different. Accordingly, the pump light polarization control unit 40 generates a control signal so that the optical intensity of the X polarization component and the Y polarization component of the optically regenerated polarization orthogonal multiplexed signal becomes the same, and the polarization controller 13 is output. That is, in this embodiment, the polarization state observation unit 43 calculates a difference value between the light intensity of the X polarization component and the light intensity of the Y polarization component output from the PBS 42. Based on the difference value from the polarization state observation unit 43, the control signal generation unit 44 generates and outputs a control signal for the polarization controller 13 so that the difference value is set to “0” which is a target value.

  In the case of monitoring the optically regenerated signal light (output light of the BPF 19) as in the present embodiment, the optical recirculation circuit 20 is connected between the PBS 16 and the optical circulator 15, and from the optical circulator to the BPF 19, the light. The transmission path (see reference numeral 600) through the coupler 41 to the PBS 42 must be configured with a polarization maintaining fiber (PMF). This is because the polarization multiplexed signal regenerated at the monitor location is again polarized and the light intensity of the X polarization component and the Y polarization component is observed. This is because the axis of the PBS 16 of the circuit 20 needs to be the same.

  Next, a second embodiment of the present invention will be described. In the first embodiment, the pump light generation circuit 12 generates pump light that is continuous light (CW light) having a wavelength λp different from the wavelength λs of the signal light. Therefore, here, optical 2R reproduction is realized. In the second embodiment, clock light is used as pump light. Therefore, in the second embodiment, optical 3R reproduction is realized. In the second embodiment, optical signal processing is used to generate clock light. However, it is also possible to generate clock light using electrical signal processing as will be described later.

  As will be described in detail below, when clock light is acquired using optical signal processing, it is possible to generate a clock signal using injection locking of a mode-locked laser (MLLD). In the present embodiment, the wavelength of the signal light is equal to the wavelength of the clock signal. However, in order to perform optical regeneration by applying parametric amplification, it is necessary that the wavelength of the clock light and the wavelength of the signal light be different. Therefore, it is necessary to perform wavelength conversion in any form. Also in the present embodiment, for example, necessary wavelength conversion such as wavelength conversion by optical signal processing using four-wave mixing (FWM) is performed.

  FIG. 7 is a block diagram showing the configuration of the optical regenerator according to the second embodiment of the present invention. In FIG. 7, the same components as those of the optical regenerating apparatus according to the first embodiment shown in FIG. As shown in FIG. 7, the optical regenerator 50 according to the second embodiment has an optical coupler 51 that demultiplexes signal light, and pump light that is clock light by inputting the signal light from the optical coupler 51. A pump light generation circuit 52 is provided.

  FIG. 8 is a block diagram showing details of the pump light generation circuit according to the second embodiment. As shown in FIG. 8, the pump light generation circuit 52 includes a wavelength conversion light source 61, a mode-locked laser (MLLD) 62, a wavelength conversion device 63, a band pass filter (BPF) 64, and a delay line 65. . In the pump light generation circuit 52, signal light is incident on the MLLD 62 to generate pump light (clock light) based on the signal light. In MLLD, clock light synchronized with data modulation of signal light is generated. In the present embodiment, the wavelength of the pump light is λs that is the same as the wavelength of the signal light.

  Further, the wavelength conversion light source 61 outputs continuous light (CW light) having a wavelength λp. The pump light from the MLLD 62 and the continuous light from the wavelength conversion light source 61 are given to the wavelength conversion device 63.

  The wavelength conversion device 63 is composed of, for example, a highly nonlinear fiber (HNLF), and realizes wavelength conversion by optical signal processing using four-wave mixing (FWM). Thereby, the wavelength λs of the pump light from the MLLD 62 is converted into the wavelength λp from the wavelength conversion light source 61. As a result, the wavelength conversion device 63 outputs the clock light having the wavelength λp. The clock light output from the wavelength changing device 63 is applied to the BPF 64, and only the light having the wavelength λp is extracted from the BPF 64. Thereafter, the timing is synchronized with the signal light through the delay line 65, and the pump light generation circuit 52 is supplied. Is output from. The pump light (clock light) output from the pump light generation circuit 52 passes through the polarization controller 13 and is combined with the signal light in the optical coupler 14.

  The configurations and functions of the optical circulator 15, the optical regenerative loop circuit 20, the BPF 19, the polarization controller 11, and the polarization controller 13 in the second embodiment are the same as those in the first embodiment.

  Next, modifications of the components in the optical repeater according to the present embodiment will be described. First, another configuration example for realizing the function of the optical circulator will be described. The optical circulator 15 used in the first embodiment and the second embodiment outputs light received from each port from one predetermined adjacent port. The function of the optical circulator 15 can also be realized by using an optical isolator and an optical coupler.

  FIG. 9 is a block diagram showing the configuration of the optical regenerator according to the third embodiment of the present invention. In FIG. 9, the same components as those of the optical regenerators according to the first and second embodiments are denoted by the same reference numerals. Further, in the optical regenerator according to the third embodiment, the pump light generation circuit 12 outputs continuous light pump light as in the first embodiment, but is not limited thereto. As in the second embodiment, pump light of clock light may be output.

  As shown in FIG. 9, the optical regenerator 70 according to the third embodiment accepts the light output from the optical coupler 14 and outputs it in a predetermined direction, and returns from the optical regenerative loop circuit 20. An optical path determination unit 71 that outputs light in another predetermined direction is provided. The optical path determination unit 71 includes an optical isolator 72 and an optical coupler 73. The optical isolator 73 is disposed between the optical coupler 14 and the optical coupler 73, and is configured to output only light in one direction, that is, light output from the optical coupler 14 to the optical isolator 73. On the other hand, the light from the optical coupler 73 is blocked and is not output to the optical coupler 14 side.

  For example, when the optical intensity of an optical signal incident on two input ports is a and b, the 2-input 2-output optical coupler has (a + b) / 2 and (a + b) / 2 on the two output ports, respectively. It has the property of outputting light intensity. Utilizing this, the optical isolator 73 according to the present embodiment uses the optical coupler 73 as described above as one input and two outputs, makes light from the optical isolator 72 incident on one input port, and uses this. Output to the optical regeneration loop circuit 20. On the other hand, when the light output from the optical regenerative loop circuit 20 is applied to the optical coupler 73, 1/2 of the light is output to the BPF 19, and the remaining 1/2 is output to the optical isolator 72 side. In the optical isolator 72, the light from the optical coupler 73 is blocked. On the other hand, as for the light output to the BPF 19, only the signal of the wavelength λs is extracted and output from the BPF.

  Next, another example of the PBS in the optical regeneration loop circuit will be described. As shown in FIG. 3, in the first embodiment and the second embodiment, in the PBS 16, the polarization signals of 0 ° (horizontal) and 90 ° (vertical) of the input signal of the polarization orthogonal multiplexed signal are polarized. The state is output as 0 ° and 90 ° polarization states at the two output ports. On the other hand, as described above, in PBS, the polarization state of 0 ° or 90 ° of the input / output signal of the polarization orthogonal multiplexed signal is the polarization state in which both of the two output ports are 0 ° or 90 °. Some are output.

  As described above, the case where the PBS in which one component is output by being rotated by 90 ° will be described. As shown in FIG. 10, in the optical regeneration loop 120, at the input port of the PBS 116, the signal light is polarized at 0 ° (X polarization) indicated by a solid line and 90 ° polarization (Y polarization) indicated by a broken line. (See reference numeral 300). The PBS 116 outputs light that propagates through the optical regeneration loop counterclockwise, corresponding to the Y polarization component at the input port (see reference numeral 1001). As indicated by reference numeral 1001, the polarization state of this light is rotated by 90 ° by the PBS 116. Further, the PBS 116 outputs light propagating in the light regeneration loop in a clockwise direction corresponding to the X polarization component at the input port (see reference numeral 1002). This light is output as it is without being rotated.

  A case where the polarization state of propagating light (X-polarized light and Y-polarized light) is maintained in the jumper cable constituting the optical regeneration loop of the optical regeneration loop circuit 120 and in the regeneration circuit 18. Think. For example, this is a case where the jumper cable and the highly nonlinear fiber (HNLF) constituting the regenerative circuit 18 are configured by polarization maintaining fibers (PMF). In this case, the polarization input at 0 ° (90 °) propagates with 0 ° (90 °). Since the polarization directions of the two output ports of the PBS 116 are the same, the signal output from one side of the PBS 116 can be directly input to the other port as it is. That is, there is no need for polarization adjustment in the optical regeneration loop.

  On the other hand, when the jumper cable constituting the optical regeneration loop and the regeneration circuit 18 are not composed of PMF, light propagating in the optical regeneration loop counterclockwise and light propagating in the optical regeneration loop clockwise are Both are in an arbitrary polarization state. Therefore, in this case, as described with reference to FIG. 4, the polarization adjustment circuit 121 is arranged in the optical regeneration loop. The polarization adjustment circuit 121 includes, for example, one or more λ / 2 plates and λ / 4 plates, and appropriately sets the polarization state by setting the λ / 2 plates and λ / 4 plates to a predetermined angle. Control.

  Next, another configuration example of the signal light polarization control unit will be described. FIG. 11 is a block diagram including another configuration example of the signal light polarization controller that generates a control signal to the polarization controller 11 of the signal light according to the present embodiment. As shown in FIG. 11, the signal light polarization control unit 80 includes an optical coupler 81 disposed between the PBS 16 and the polarization control circuit 17 in the optical regeneration loop of the optical regeneration loop circuit 20, and the optical coupler 81. A band-pass filter (BPF) 82 that extracts light of wavelength λs from the demultiplexed light, a polarization state observation unit 83, and a control signal generation unit 84 are provided.

  In the signal light polarization control unit 80 shown in FIG. 11, the light from the output port of the PBS 16 is extracted through the optical coupler 81 and the BPF 82, the signal light having the wavelength λs is extracted, and the extracted signal light having the wavelength λs is polarized. This is given to the state control unit 83. The polarization state control unit 83 and the control signal generation unit 84 operate in the same manner as the polarization state control unit 33 and the control signal generation unit 34 illustrated in FIG. That is, the polarization control state observation unit 83 includes an optical receiver and a power observation unit, and outputs a signal indicating the power state to the control signal generation unit 84. The control signal generator 84 receives a signal indicating the power state and outputs a control signal to the polarization controller 11 so that the power decreases. The polarization controller 11 rotates the angles of the λ / 2 plate and the λ / 4 plate according to the control signal.

  In the optical regenerator provided with the signal light polarization control unit 80 shown in FIG. 11, the signal light monitor point is between the PBS 16 and the polarization control circuit 17 in the light regeneration loop. Therefore, it is not necessary to configure a jumper cable or the like between the polarization controller 11 and the optical coupler 81 of the optical regeneration loop circuit 20 with a polarization maintaining fiber (PMF).

  Next, another configuration example of the pump light polarization control unit will be described. FIG. 12 is a block diagram including another configuration example of the pump light polarization controller that generates a control signal to the polarization controller 13 of the signal light according to the present embodiment. As shown in FIG. 12, the pump light polarization control unit 90 includes an optical coupler 91 disposed between the PBS 16 and the polarization control circuit 17 in the optical regeneration loop of the optical regeneration loop circuit 20, and an optical coupler 91. A band pass filter (BPF) 92 for extracting light of wavelength λp from the demultiplexed light, an optical coupler 93 disposed between the PBS 16 and the regeneration circuit 18 in the optical regeneration loop, and demultiplexing by the optical coupler 93. A band-pass filter (BPF) 94 that extracts light of wavelength λp from the emitted light, a polarization state observation unit 95, and a control signal generation unit 96 are provided.

  In the pump light polarization controller 90 configured as described above, the light intensity of light output from the two output ports of the PBS 16 is observed, and the polarization controller 13 is controlled so that the light intensity of both is equal. The polarization state observation unit 95 measures the light intensity of the optical signals from the BPF 92 and the BPF 94 and calculates the difference value. Based on the difference value from the polarization state observation unit 95, the control signal generation unit 96 generates and outputs a control signal for the polarization controller 13 so that the difference value is set to the target value “0”.

  In the optical regenerator provided with the pump light polarization control unit 90 shown in FIG. 12, the pump light monitor point is in the light regenerative loop. Therefore, it is not necessary to configure a jumper cable or the like extending between the polarization controller 13 and the optical couplers 91 and 93 of the optical regeneration loop circuit 20 with a polarization maintaining fiber.

  Next, another configuration example of the pump light generation circuit according to the second embodiment will be described. In the pump light generation circuit shown in FIG. 8, pump light that is clock light is generated by optical signal processing. In another configuration example shown in FIG. 13, pump light that is clock light is generated by electric signal processing. ing. As illustrated in FIG. 13, the pump light generation circuit 52 includes an optical receiver 131, a clock recovery circuit 132, a mode-locked laser (MLLD) 133, and a delay line 134. In the pump light generation circuit 52 of FIG. 13, a signal line (reference numeral 135) from the output of the optical receiver 131 to the input of the MLLD 133 is a signal line of an electric signal.

  In the pump light generation circuit 52 shown in FIG. 13, the optical receiver 131 photoelectrically converts signal light to obtain an electrical signal. Next, the clock recovery circuit 132 obtains a clock signal synchronized with the data modulation of the signal light. By driving the MLLD 133 with a clock signal based on an electrical signal, pump light that is clock light can be obtained. The obtained pump light is output from the pump light generation circuit 52 in synchronization with the signal light through the delay line 134. The pump light (clock light) output from the pump light generation circuit 52 passes through the polarization controller 13 and is combined with the signal light in the optical coupler 14.

  Next, a fourth embodiment of the present invention will be described. In the second embodiment of the present invention, the pump light generation circuit 52 generates pump light that is clock light based on the signal light input to the optical regenerator, that is, the signal light before being optically regenerated. ing. In the optical regenerator according to the fourth embodiment, the pump light generation circuit 52 generates pump light based on the signal light after optical regeneration.

  FIG. 14 is a block diagram showing the configuration of the optical regenerator according to the fourth embodiment of the present invention. In FIG. 14, the same components as those of the optical regenerating apparatus according to the second embodiment shown in FIG. As shown in FIG. 14, the optical regenerator 140 according to the fourth embodiment includes an optical coupler 141 that demultiplexes the regenerated signal light output from the BPF 19, and the signal output from the optical coupler 141. Light enters the pump light generation circuit 52. The pump light generation circuit 52 may be the one shown in FIG. 8 or the one shown in FIG.

  FIG. 15 is a block diagram illustrating an example in which the optical regeneration system according to the present embodiment is applied to a polarization multiplexing transmission system. In this example, a repeater including the optical regenerator according to the present embodiment is arranged at a predetermined relay location of the polarization multiplexing transmission system to regenerate an optical signal with deteriorated transmission quality and extend the transmission distance. I'm crazy. In the example of FIG. 15, the optical signal from the transmitter TX of the transmission apparatus 1500 is polarization multiplexed in the polarization multiplexing device and sent to the transmission line 1501. The relay device 1502 arranged in the transmission line 1501 has the optical regenerator 10, regenerates an optical signal whose transmission quality has deteriorated, and outputs it again to the transmission line. In the receiver 1503, the signal light is separated by the polarization separation device, and each signal light is received by the receiver RX.

  In particular, the transmission can be expanded to polarization multiplexing transmission by changing the transmitter and the receiver for large-capacity transmission from conventional transmission using polarization in a single direction. However, at that time, in the polarization multiplexing transmission, there is a possibility that the transmittable distance is shortened due to the influence of the polarization crosstalk. In order to cope with this, by arranging the repeater including the optical regenerator according to the present embodiment, it becomes possible to compensate for the reduced transmission distance and to install the transmission / reception system at the same position as the conventional one.

  The optical reproducing apparatus according to the present embodiment can also be applied to WDM signals. However, since the optical regenerator according to the present embodiment can reproduce light only for a single wavelength, it cannot be directly applied to a multi-wave signal such as WDM. is there. Therefore, as shown in FIG. 16, the repeater 1601 performs wavelength demultiplexing before signal processing, and the optical regenerator for each wavelength regenerates the signal light of the corresponding wavelength. With such a configuration, the optical reproducing apparatus according to the present embodiment can be applied to a WDM signal.

  The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

  For example, the optical reproducing apparatus according to the present invention can be applied to a phase modulation signal. In a general optical reproduction method, the amplitude has a noise reduction effect, but the phase information has a characteristic of deteriorating. On the other hand, in the present embodiment, parametric amplification is used for optical regeneration, which has a noise reduction effect on the amplitude and can retain the phase information without deterioration. For this reason, it is applicable to a phase modulation signal.

  In particular, in recent years, there have been many reports of realizing long-distance and large-capacity transmission with high frequency utilization efficiency using a polarization multiplexed signal and a four-phase phase modulation method (DQPSK modulation). Be expected.

  Two types of polarization multiplexed signals are known: an interleave type and a non-interleave type. The optical regenerator according to the present invention can be applied to any type of polarization multiplexed signal. For the non-interleaved type, the positions of the X polarization and Y polarization bits coincide. On the other hand, the interleave type is a method in which the positions of the X-polarized wave and Y-polarized bit do not match and are shifted by half a bit. In this case, the interference detection method cannot be used for polarization state observation and control signal generation. Therefore, in the case of non-interleave, it is possible to control by monitoring the power of the clock component of the electric signal.

  In the second embodiment, the wavelength of the signal light is equal to the wavelength of the clock signal. However, the present invention is not limited to this, and can be realized even when the wavelength of the signal light and the wavelength of the clock signal are not the same when acquiring a signal using MLLD injection locking. FIG. 17 is a diagram illustrating another example of the pump light generation circuit. As shown in FIG. 17, in this example, the pump light generation circuit 52 includes an MLLD 62 and a delay line 65. In the pump light generation circuit 52 shown in FIG. 17, when the wavelength of the signal light and the clock light are not the same and the clock light has a desired wavelength as the pump light, wavelength conversion is not necessary. If the wavelengths are not the same but are not desired as the pump light, or if the wavelengths are the same as shown in FIG. 8, wavelength conversion is required.

FIG. 1 is a block diagram showing the configuration of the optical regenerator according to the first embodiment of the present invention. 2A is a diagram illustrating an example of the wavelengths of the signal light and the pump light, FIG. 2B is a diagram illustrating the polarization state of the signal light and the pump light at the input port 101 of the PBS 16, and FIG. (D) is a figure which shows the polarization state of the signal light and pump light in the output ports 102 and 103 of PBS16, respectively. FIG. 3 is a diagram illustrating an example of a polarization state of light in the present embodiment. FIG. 4 is a diagram illustrating another example of the polarization state of light in the present embodiment. FIG. 5 is a block diagram including a signal light polarization control unit that generates a control signal to the polarization controller 11 of the signal light according to the present embodiment. FIG. 6 is a block diagram including a pump light polarization controller that generates a control signal to the polarization controller 13 of the signal light according to the present embodiment. FIG. 7 is a block diagram showing the configuration of the optical regenerator according to the second embodiment of the present invention. FIG. 8 is a block diagram showing details of the pump light generation circuit according to the second embodiment. FIG. 9 is a block diagram showing the configuration of the optical regenerator according to the third embodiment of the present invention. FIG. 10 is a diagram illustrating still another example of the polarization state of light in the present embodiment. FIG. 11 is a block diagram including another configuration example of the signal light polarization controller that generates a control signal to the polarization controller 11 of the signal light according to the present embodiment. FIG. 12 is a block diagram including another configuration example of the pump light polarization controller that generates a control signal to the polarization controller 13 of the signal light according to the present embodiment. FIG. 13 is a block diagram showing another configuration example of the pump light generation circuit according to the second embodiment. FIG. 14 is a block diagram showing the configuration of the optical regenerator according to the fourth embodiment of the present invention. FIG. 15 is a block diagram illustrating an example in which the optical regeneration system according to the present embodiment is applied to a polarization multiplexing transmission system. FIG. 16 is a block diagram showing another example in which the optical regeneration system according to the present embodiment is applied to a polarization multiplexing transmission system. FIG. 17 is a diagram illustrating another example of the pump light generation circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical regenerator 11 Polarization controller 12 Pump light generation circuit 13 Polarization controller 14 Optical coupler 15 Optical circulator 16 PBS
17 Polarization adjustment circuit 18 Reproduction circuit 19 BPF
20 Optical loop regeneration circuit

Claims (12)

An optical regenerator that propagates a transmission line and receives signal light of a polarization orthogonal multiplexed signal in which two optical signals of orthogonal polarization states are multiplexed by polarization multiplexing transmission, and reproduces and outputs the signal light Because
Pump light generating means for generating pump light having a wavelength λp different from the wavelength λs of the signal light;
First polarization control means for controlling the polarization state of the signal light;
Second polarization control means for controlling the polarization state of the pump light;
Multiplexing means for multiplexing the signal light output from the first polarization control means and the pump light output from the second polarization control means;
The combined light from the multiplexing means is received at the input port, and the first polarized wave component and the second polarized wave component orthogonal to the first polarized wave component are output from the combined light into two outputs. A polarization beam splitter that outputs to a port, an optical regeneration loop that is a transmission path in which the two output ports are connected in a loop, and the first polarization component and the second An optical regeneration loop means having a reproducing means for parametrically amplifying the polarization component of
Propagating through the light regeneration loop of the light regeneration loop means, recombined in the polarization beam splitter, and received the regenerated combined light output from the input port of the polarization beam splitter, Bandpass filter means for passing light of wavelength λs;
At least three ports are connected to each of the multiplexing means, the optical regeneration loop means, and the band pass filter means, and the combined light from the multiplexing means is output to the optical regeneration loop means And an optical path determining means for outputting the regenerated combined light from the optical regeneration loop means to the band pass filter means. The first polarization control means indicates the polarization state of the signal light, and the first polarization component of the polarization orthogonal multiplexed signal is linearly polarized with respect to a first axis of the polarization beam splitter. As well as controlling
The second polarization control means is configured to change a polarization state of the pump light with respect to the first axis in the polarization beam splitter when combined light including the pump light is input to the polarization beam splitter. The optical reproducing apparatus according to claim 1, wherein the optical reproducing apparatus is controlled so as to be 45-degree linearly polarized light.   2. The optical regeneration loop means includes polarization adjustment means that is disposed on the optical regeneration loop and adjusts the polarization states of the first polarization component and the second polarization component. Or the optical reproduction apparatus of 2. The polarization beam splitter is configured such that the polarization state of the input combined light is maintained and the first polarization component and the second polarization component are output from the two output ports. ,
The jumper cable constituting the optical regeneration loop, and the regeneration means are configured to maintain the polarization state; and
4. The light according to claim 3, wherein the polarization adjusting unit is configured to rotate the respective polarization states of the received first polarization component and second polarization component by 90 degrees. Playback device. The first polarization component is output from the first output port of the polarization beam splitter, propagates on the optical regeneration loop, and is input to the polarization beam splitter again at the second port of the polarization beam splitter. The second polarization component is output from the second output port, propagates on the optical regeneration loop, and is input again to the polarization beam splitter at the first port of the polarization beam splitter;
The polarization adjusting means is
When the first polarization component is input to the polarization beam splitter again at the second port, the second polarization component when the polarization state is output from the second port And the same polarization state, and
When the second polarization component is input to the polarization beam splitter again at the first port, the first polarization component when the polarization state is output from the first port 4. The optical regenerator according to claim 3, wherein the polarization states of the first polarization component and the second polarization component are controlled so as to be the same as the polarization state of the first polarization component. Wherein the outputs of the polarization beam splitter, one of only polarization states of the polarization components is rotated 90 °, and,
The optical regenerator according to claim 1 or 2, wherein the jumper cable constituting the optical regenerative loop and the regenerating unit are configured to maintain polarization. Signal light polarization control means for generating a first control signal for the first polarization control means,
First demultiplexing means disposed between the first polarization control means and the multiplexing means;
A first polarization state observation unit that receives the signal light demultiplexed by the first demultiplexing unit and calculates an index value based on a polarization state of the signal light; and the first polarization state observation Signal light control signal generating means for generating a first control signal for controlling the first polarization control means based on the index value calculated by the means so as to optimize the index value. With signal light polarization control means,
From the output port of the first polarization control means to the input port of the polarization beam splitter of the optical regeneration loop means via the first demultiplexing means, the multiplexing means, and the optical path determining means The optical regenerating apparatus according to claim 1, wherein the optical path is configured to maintain the polarization. Signal light polarization control means for generating a first control signal for the first polarization control means,
In the light regeneration loop means, first demultiplexing means disposed on the light regeneration loop from one output port of the polarization beam splitter;
A first polarization state observation unit that receives the signal light demultiplexed by the first demultiplexing unit and calculates an index value based on a polarization state of the signal light; and the first polarization state observation Signal light control signal generating means for generating a first control signal for controlling the first polarization control means based on the index value calculated by the means so as to optimize the index value. 7. The optical regenerating apparatus according to claim 1, further comprising a signal light polarization control unit. Pump light polarization control means for generating a second control signal for the second polarization control means,
Second demultiplexing means disposed on the optical transmission line from the output port of the bandpass filter means;
A polarization acquisition unit that receives the regenerated signal light demultiplexed by the second demultiplexing unit and acquires respective polarization components of the signal light; and a polarization acquired by the polarization acquisition unit. Second polarization state observation means for calculating an index value based on the light intensity of each of the wave components, and the second polarization state observation means so that the index value calculated by the second polarization state observation means is optimal. A pump light polarization control means having a pump light control signal generation means for generating a second control signal for controlling the polarization control means of
Optical path from the input port of the polarization beam splitter of the optical regeneration loop means to the polarization acquisition means via the optical path determination means, the band pass filter means, and the second demultiplexing means The optical regenerator according to claim 1, wherein the optical regenerator is configured to maintain the polarization. Pump light polarization control means for generating a second control signal for the second polarization control means,
A second demultiplexing means and a third demultiplexing means respectively disposed on the optical regeneration loop from the two output ports of the polarization beam splitter of the optical regeneration loop;
Second polarization state observing means for calculating an index value based on the light intensity of each of the polarization components of the combined light , demultiplexed by the second demultiplexing means and the third demultiplexing means, A pump light control signal generating means for generating a second control signal for controlling the second polarization control means so that the index value calculated by the second polarization state observing means becomes optimal. 9. The optical regenerator according to claim 1, further comprising pump light polarization control means having the optical pump polarization control means.   11. The optical regenerator according to claim 1, wherein the pump light generation unit generates continuous light having the wavelength λp.   11. The optical regeneration according to claim 1, wherein the pump light generation unit receives the signal light and generates pump light that is clock light synchronized with data modulation of the signal light. apparatus.

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