JP5396301B2 - Optical path length adjusting method and apparatus for optical line - Google Patents

Description

  The present invention relates to a low-loss optical path length adjustment technique capable of continuously changing the optical path length of an optical line constituted by an optical fiber.

  For example, this technology can be used to provide a means to carry out the construction of the working communication line without disrupting the service by preparing a bypass line for the working communication line using optical fiber and temporarily duplicating the line. The present invention can be applied to an optical line maintenance system or the like for adjusting the optical path length difference between the communication line and the detour line so as not to affect the communication. In this case, the present invention relates to a technique for adjusting the optical path length with low loss by providing a duplex optical line in the detour line.

  2. Description of the Related Art In recent years, service uninterruptible switching technology has been developed that allows a communication service to be transferred from a working line to a transfer destination line without disrupting a communication service in an optical fiber line trouble transfer work or the like (for example, Non-Patent Document 1). reference.).

  In this technology, a bypass line is prepared and temporarily duplicated with the active line, and then the communication line is transmitted only by the bypass line, thereby enabling construction of the active line. At that time, in order to duplicate the line while maintaining the communication service, it is necessary to keep the optical path length difference between the working line and the detour line within the specified error range. Therefore, means to adjust the optical path length to the detour line is indispensable. Become.

  For this reason, a method has been proposed in which an optical space optical system that spatially propagates an optical signal propagating through an optical fiber by a pair of collimators and the optical path length is adjusted by continuously changing the distance between the collimators. At that time, since the extension distance by the spatial optical system is not necessarily sufficient to directly cover the difference in optical path length between the working and detour lines, a method of successively accumulating a fixed extension distance by the spatial optical system is adopted. (For example, refer nonpatent literature 1.).

  This is because the optical path corresponding to this fixed length is inserted into the optical path on the other side after extending a fixed length optical path length by a spatial optical system provided on one side with a duplex optical line in the detour line. The optical path length of the detour line is successively extended by repeatedly performing the operation of shifting and changing the optical signal while equalizing.

  However, since this duplex line is coupled by a wavelength-independent optical coupler, for example, when coupled at a branching ratio of 50:50, a loss of 6 dB or more is generated only by these two couplers. In addition, when a level difference of 6 dB or more is given between two optical lines in order to stably duplicate the optical signal, there is a problem that the loss further increases in the line on the side where the optical power is weak.

Higashi et al., IEICE Technical Report OFT2008-52 "Fundamental study of optical access medium switching system-Service uninterrupted optical medium switching system" The Institute of Electronics, Information and Communication Engineers, 2008, pp.27-31 L. Yan, et al., Programmable Group-Delay Module Using Binary Polarization Switching, Journal of Lightwave Thechnology, vol. 21, no. 7, July 2003, pp. 1676-1684.

  An object of the present invention is to change the branching ratio of a duplex optical line composed of a polarization maintaining optical fiber formed between a pair of input polarization separation couplers and an output polarization synthesis coupler in a detour line by a polarization controller. An optical path length adjusting method and apparatus for an optical line that adjusts the optical path length with low loss by changing the optical path length while providing the optical path length.

In order to achieve the above object, an optical path length adjusting device of an optical line according to the present invention is a duplexed optical line comprising a polarization maintaining optical fiber configured between a pair of input polarization separating couplers and an output polarization combining coupler. Are coupled to the two outputs of the polarization splitter coupler for input via a polarization controller that changes the branching ratio, respectively, and each of the optical signals of the two optical lines is decomposed by the polarization separator coupler and each of the x-axis and Coupled via two-input, two-output input side polarization demultiplexer that alternately synthesizes y-axis components using a polarization combiner and a polarization controller that changes the branching ratio to the two inputs of the output polarization combiner. A two-input two-output output side polarization demultiplexer / synthesizer that separates the optical signals of the two optical lines with a polarization decoupler and alternately synthesizes the x-axis and y-axis components with a polarization combiner. And an optical fiber switching device capable of changing the optical line length disposed in each of the duplex optical lines between the input side polarization beam splitter / combiner and the output side polarization beam splitter / combiner in a predetermined length step, A continuous optical path length adjusting device capable of continuously adjusting the optical path length within a range including the predetermined length, provided in at least one of the duplex optical lines between the input side polarization splitter / combiner; It is characterized by comprising.

  Further, the present invention is characterized in that in the optical path length adjusting device for the optical line, the continuous optical path length adjusting device is omitted, and a variable DGD (differential group delay) generator is provided on the output port side of the output polarization combining coupler. It is what.

An optical path length adjustment method for an optical line according to the present invention uses the optical path length adjustment device for an optical line according to claim 2 , and the polarization controller changes the branching ratio of the duplex optical line from one optical line to the other optical line. A first step of changing the optical power to conduct, a second step of increasing the unit length of the optical path in the optical fiber switching device in which the optical power of the duplexed optical line is not conducted, and the duplexed light beam A third step of inverting the polarity of the DGD corresponding to half of the unit length with a variable DGD generator connected to the polarization combining coupler for output of the path, and repeating the first step to the third step The optical path length is extended by.

  The present invention is an optical path length adjusting device for a duplexed optical line in a detour line, and a duplexed optical line comprising a polarization maintaining optical fiber configured between a pair of input polarization separating couplers and an output polarization combining coupler. The branching ratio is changed by a polarization controller. By performing the routing of the duplexed optical line by polarization control, it becomes possible to extend the optical path length as a whole while alternately extending the optical path lengths of the two optical lines in predetermined unit length steps. At this time, there is no loss that occurs in the case of a duplex line using an optical power branching coupler.

  Moreover, since the power branching ratio is continuously controlled by the polarization controller, there is no sudden level fluctuation that occurs in route switching by simple ON / OFF of an optical switch. This can provide a low-loss optical path length adjustment mechanism that adjusts the optical path length difference from the active line to the detour line required for temporarily duplicating the line, for example, when work on the active line is required, such as trouble relocation. .

1 is an explanatory diagram illustrating a configuration of an optical path length adjusting device for an optical line according to a first embodiment of the present invention. It is composition explanatory drawing which shows the optical path length adjustment apparatus of the optical line which concerns on the 2nd Embodiment of this invention. It is composition explanatory drawing which shows the modification of the optical path length adjustment apparatus of the optical line which concerns on the 2nd Embodiment of this invention. It is composition explanatory drawing which shows the optical path length adjustment apparatus of the optical line which concerns on the 3rd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is an explanatory diagram showing a configuration of an optical path length adjusting device for an optical line according to the first embodiment of the present invention. In FIG. 1, 11 is an input port, 12 is a polarization controller, 13 is an input polarization separation coupler, 14 is a first collimator, 15 is a second collimator, 16 is a mirror, 17 is an optical fiber switching device, 18 Is an output polarization combining coupler, 19 is an optical fiber switching device, 20 is an output port, 21 is a continuous optical path length adjusting device, and 22 is a polarization maintaining optical fiber.

  As shown in FIG. 1, the input port 11 is connected to the input end of the input polarization separation coupler 13 via the polarization controller 12, and one output end of the input polarization separation coupler 13 is connected to the first collimator 14. Connected to the input terminal. The input surface of the mirror 16 is disposed at a position facing the output end of the first collimator 14, and the input end of the second collimator 15 is disposed at a position facing the output surface of the mirror 16. The output end of the second collimator 15 is connected to the input end of the optical fiber switching device 17, and the output end of the optical fiber switching device 17 is connected to one input end of the output polarization combining coupler 18.

  The other output end of the input polarization separation coupler 13 is connected to the input end of the optical fiber switching device 19, and the output end of the optical fiber switching device 19 is connected to the other input end of the output polarization combining coupler 18. Is done. The output end of the output polarization beam combiner 18 is connected to the output port 20. The collimators 14 and 15 and the mirror 16 constitute a continuous optical path length adjusting device 21, and the mirror 16 is provided movably in the direction of the arrow with a stroke of 0.5 m. A polarization maintaining optical fiber 22 is formed between the input polarization separation coupler 13 and the output polarization combining coupler 18, and a linearly polarized wave A route passing through the continuous optical path length adjusting device 21 and the optical fiber switching device 17, and a light. It is divided into the linearly polarized wave B route passing through the fiber switching device 19.

  That is, between the pair of input polarization separating coupler 13 and output polarization combining coupler 18, a duplex optical line is formed by the polarization maintaining optical fiber 22, and the length of the optical line is set to a predetermined length for each line. For example, optical fiber switching devices 17 and 19 capable of selecting optical fibers having different lengths at intervals of 1 m are arranged.

  At least one of the duplexed optical lines is provided with a continuous optical path length adjusting device 21 capable of continuously adjusting the optical path length within a range including the predetermined length. For example, an optical space optical system is disposed on one side of the optical line (A route). The optical signal propagating through the optical fiber is converted into spatial light by the collimator 14, reflected by the mirror 16, and guided again to the optical fiber by the other collimator 15. The optical path length of the A route can be continuously changed by changing the position of the mirror 16.

  A polarization controller 12 is provided on the input port 11 side of the input polarization separation coupler 13 to convert input light in an arbitrary polarization state into linearly polarized light, and further control the inclination of the linearly polarized wave to obtain the A route. And the optical power branching ratio of B route can be changed.

  If the input polarization separation coupler 13 separates the x-axis component and the y-axis component and couples them to the polarization maintaining optical fibers 22 of the A route and the B route, respectively, the polarization controller 12 converts them into linearly polarized waves. By making the polarization axis of the converted input light parallel to the x-axis, the optical power can be conducted only to the A route.

  When the distance between the collimators 14 and 15 and the mirror 16 is extended from 0 to 0.5 m with the selection of the optical fiber switching device 17 for the A route being 0 m, the optical path length of the A route is increased by 1 m. At this time, if the optical fiber switching device 19 for the B route is set to 1 m, the optical path lengths of the two routes coincide with each other. Therefore, even if the angle of the linearly polarized light by the polarization controller 12 is changed in the y-axis direction, both routes are Since the optical signal recombined by the output polarization combining coupler 18 via the delay difference due to duplexing can be ignored, the communication is not affected.

  If the direction of linearly polarized light coincides with the y-axis, the optical power can be conducted only to the B route. During this time, the selection of the optical fiber switching device 17 for the A route is switched to 1 m, and between the collimators 14 and 15 and the mirror 16. If the distance is set to 0 m, the optical path length of the two routes does not change. Therefore, if the direction of the linearly polarized light by the polarization controller 12 is adjusted to the x axis, the optical power is again conducted only to the A route.

  With these series of operations, the optical path length is extended by 1 m while maintaining the communication state from the initial state. By repeating this, the optical path length can be further extended. In this way, since the input light is separated and recombined by the input polarization demultiplexing coupler 13 and the output polarization combining coupler 18, no loss occurs in the case of the duplex line by the optical power branching coupler.

  Further, since the power branching ratio is continuously controlled by the polarization controller 12, there is no abrupt level fluctuation that occurs in route switching by simple ON / OFF of an optical switch. Note that even if the physical lengths of the A route and the B route are matched, the propagation times of the optical signals are not necessarily matched, but for example, the propagation times at the time of duplexing are matched by a method using optical interference. This can be solved by storing the correct mirror position in advance.

  On the other hand, in this method, the polarization state of the input light is converted into linearly polarized light by the polarization controller 12, but if the polarization state of the input light changes abruptly, the control of the polarization state cannot catch up and two routes are desired. The optical power cannot be conducted at a branching ratio of. An optical path length extension method using a duplex optical line in this case will be described below.

  FIG. 2 is an explanatory diagram showing a configuration of an optical path length adjusting device for an optical line according to the second embodiment of the present invention. In FIG. 2, 31 is an input port, 32 is an input polarization separation coupler, 33 is a polarization controller, 34 is a polarization separation coupler, 35 is a polarization combining coupler, 36 is a first collimator, 37 is a mirror, 38 Is a second collimator, 39 is an optical fiber switching device, 40 is a polarization separating coupler, 41 is a polarization combining coupler, 42 is a polarization controller, 43 is a polarization combining coupler for output, 44 is a polarization controller, and 45 is Polarization decoupler, 46 is a polarization combiner, 47 is an optical fiber switching device, 48 is a polarization decoupler, 49 is a polarization combiner, 50 is a polarization controller, 51 is an output port, and 52 is a continuous optical path length adjustment. The apparatus, 53 is a polarization beam splitter / combiner, and 54 is a polarization beam splitter / combiner.

  As shown in FIG. 2, the input port 31 is connected to the input end of the input polarization separation coupler 32, and one output end of the input polarization separation coupler 32 is connected to the polarization separation coupler 34 via the polarization controller 33. Connected to the input terminal. One output end of the polarization separation coupler 34 is connected to one input end of the polarization combining coupler 35, and the other output end of the polarization separation coupler 34 is connected to one input end of the polarization combining coupler 46. The output terminal of the polarization beam combiner 35 is connected to the input terminal of the first collimator 36. The input surface of the mirror 37 is disposed at a position facing the output end of the first collimator 36, and the input end of the second collimator 38 is disposed at a position facing the output surface of the mirror 37. The output end of the second collimator 38 is connected to the input end of the optical fiber switching device 39, and the output end of the optical fiber switching device 39 is connected to the input end of the polarization splitting coupler 40. One output end of the polarization separation coupler 40 is connected to one input end of the polarization combining coupler 41 and the other output end of the polarization separation coupler 40 is connected to one input end of the polarization combining coupler 49. The output end of the polarization combining coupler 41 is connected to one input end of the output polarization combining coupler 43 via the polarization controller 42.

  The other output end of the input polarization separation coupler 32 is connected to the input end of the polarization separation coupler 45 via the polarization controller 44, and one output end of the polarization separation coupler 45 is connected to the polarization combining coupler 35. The other output end of the polarization splitting coupler 45 is connected to the other input end and the other input end of the polarization combining coupler 46. The output end of the polarization combining coupler 46 is connected to the input end of the optical fiber switching device 47, and the output end of the optical fiber switching device 47 is connected to the input end of the polarization splitting coupler 48. One output end of the polarization splitting coupler 48 is connected to the other input end of the polarization combining coupler 41 and the other output end of the polarization splitting coupler 48 is connected to the other input end of the polarization combining coupler 49. The output end of the polarization combining coupler 49 is connected to the other input end of the output polarization combining coupler 43 via the polarization controller 50. The output end of the output polarization combining coupler 43 is connected to the output port 51.

  The collimators 36 and 38 and the mirror 37 constitute a continuous optical path length adjusting device 52, and the mirror 37 is provided so as to be movable in the arrow direction with a stroke of 0.5 m. The polarization separation couplers 34 and 45 and the polarization combining couplers 35 and 46 constitute a polarization separation combiner 53, and the polarization separation couplers 40 and 48 and the polarization combining couplers 41 and 49 constitute a polarization separation combiner 54. To do. The route is divided into an A route passing through the continuous optical path length adjusting device 52 and the optical fiber switching device 39 and a B route passing through the optical fiber switching device 47.

  That is, between the pair of input polarization separating couplers 32 and output polarization combining couplers 43, duplex optical lines are formed by polarization maintaining optical fibers, and optical fiber switching similar to FIG. Devices 39 and 47 and a continuous optical path length adjusting device 52 are arranged. As shown in FIG. 2, a two-input two-output polarization splitting / combining unit 53 is constructed in which the outputs of two sets of polarization splitting couplers 34 and 45 are alternately combined and recombined by two sets of polarization combining units 35 and 46. The polarization beam splitter / combiner 53 is connected to the input polarization beam splitter 32 via the linear polarization controllers 33 and 44. Further, another polarization beam splitter / combiner 54 is connected to the output polarization beam combiner coupler 43 via the polarization controllers 42 and 50.

Now, an input wave having unit energy is input to the input polarization separation coupler 32, and as a result, the complex field vector when the A route and the B route are separated by the power branching ratio of r: 1-r is as follows. It can be expressed as follows.

However, φ _A and φ _B represent phase components of separated linearly polarized waves. It is assumed that the linear polarization controllers 33 and 44 are controlled to be branched by the polarization separation couplers 34 and 45 of the polarization separation combiner 53 at a power ratio of k: 1-k, respectively. At this time, as shown in the figure, the components of power ratio $ k $ are synthesized and the components of power ratio 1-k are synthesized to A route and guided to B route, so the power components of x and y axes of A route Is represented by PX and PY, respectively, in the x-axis and y-axis power components of the Px, Py, and B routes, respectively.
Px = rk, Py = k (1-r), PX = (1-r) (1-k), PY = r (1-k)

Therefore, the power ratio of the two routes is k: 1-k regardless of the polarization state of the input light. The light generated by the polarization splitting / combining unit 54 on the output side after propagating through the routes A and B is expressed as follows.

Where φ _x and φ _y represent the phase lag of light passing through the x and y axes of the A route, and φ _X and φ _Y represent the phase lag of light passing through the x and y axes of the B route. . The optical path length is extended by the same operation as in FIG. 1, but these phases are constant while the power is transferred from one route to the other in a certain duplex state. Therefore, even if the polarization state of the input wave suddenly changes and r, φ _A , and φ _B change suddenly, the polarization states of E _A ² and E _B ² do not change. On the other hand, since the polarization maintaining fiber is used in this duplex optical line, the refractive index is different between the x-axis and the y-axis, and the phase at the same point is also different. A large phase difference may cause a delay difference of an optical signal and affect communication quality. In this case, for example, if the A-axis x-axis and the B-route y-axis are selected to be the polarization-maintaining fiber fast axis, and the A-route y-axis and the B-route x-axis are the slow axes, then the signal delay difference Can be mitigated. If φ _x ≈φ _Y = φ _f and φ _X = φ _y = φ _s , E _A ² and E _B ² can be converted into the following polarization states by the polarization controller.

When the above two lights have a phase difference of φ _f -φ _s but this effect cannot be ignored, the signal delay difference due to duplexing can be eliminated by compensating by the continuous optical path length adjusting device 52.

  In the embodiment shown in FIG. 1, a spatial optical system using the collimators 14 and 15 and the mirror 16 is used as the continuous optical path length adjusting device 21. However, if the optical fiber length switching step can be reduced, for example, Non-Patent Document 2. A variable delay time adjusting device as shown in FIG. Since the light passing through one side of the duplex line is linearly polarized, it may be adjusted to one of the eigen axes of the variable delay time adjusting device. Also in the case of FIG. 2, if the configuration is changed to the configuration shown in FIG. 3, each route becomes a linearly polarized wave. Therefore, the optical path length difference of the A / B route is adjusted by using the variable delay time adjustment device as described above. be able to.

  FIG. 3 is an explanatory diagram showing a modification of the optical path length adjusting device for an optical line according to the second embodiment of the present invention. In FIG. 3, the same parts as those in FIG. In FIG. 3, 61 and 62 are variable delay time adjusting devices, and 63, 64, 65 and 66 are optical fiber switching devices.

  As shown in FIG. 3, one output end of the polarization separation coupler 34 is connected to one input end of the polarization combining coupler 41 via the variable delay time adjustment device 61 and the optical fiber switching device 63, and polarization separation is performed. The other output end of the coupler 34 is connected to the other input end of the polarization combining coupler 41 via the optical fiber switching device 65. One output terminal of the polarization separation coupler 45 is connected to one input terminal of the polarization beam combining coupler 49 via the variable delay time adjustment device 62 and the optical fiber switching device 64, and the other output terminal of the polarization beam separation coupler 45. Is connected to the other input end of the polarization beam combiner 49 via the optical fiber switching device 66.

  If the switching step can be made as small as possible so that the optical path difference length of the duplex optical line does not affect the transmission performance of the optical communication, the continuous optical path length adjusting devices 21 and 52 in FIGS. Although the delay time adjusting devices 61 and 62 can be omitted, a compensation method when this is difficult will be described in the next embodiment.

  FIG. 4 is an explanatory diagram showing a configuration of an optical path length adjusting device for an optical line according to the third embodiment of the present invention. In FIG. 4, 71 is an input port, 72 is a polarization controller, 73 is an input polarization separation coupler, 74 is a first optical switch, 75 is a second optical switch, 76 is a third optical switch, and 77 is The fourth optical switch, 78 is the fifth optical switch, 79 is the sixth optical switch, 80 is a fixed-length optical fiber having a unit length of ½, 81 is a polarization combining coupler for output, and 82 is a variable DGD (differential group delay) generator, 83 is an output port, and 84 is a polarization maintaining optical fiber.

  As shown in FIG. 4, the input port 71 is connected to the input end of the input polarization separation coupler 73 via the polarization controller 72, and one output end of the input polarization separation coupler 73 is the first optical switch. 74, the second optical switch 75, and the third optical switch 76 are connected in series to one input terminal of the output polarization combining coupler 81. The other output end of the input polarization separation coupler 73 includes a fourth optical switch 77, a fifth optical switch 78, a sixth optical switch 79, and a fixed length optical fiber 80 having a unit length of ½. It is connected to the other input end of the output polarization combining coupler 81 in series. The output end of the output polarization combining coupler 81 is connected to the output port 83 via the variable DGD generator 82. A polarization maintaining optical fiber 84 is formed between the polarization separation coupler 73 and the polarization combining coupler 81, and a linear polarization A route passing through the optical switches 74 to 76, the optical switches 77 to 79, and the fixed length optical fiber 80 are provided. Divided into the linearly polarized B route.

  That is, a duplexed optical line composed of the polarization maintaining optical fiber 84 is formed between the pair of input polarization separation couplers 72 and the output polarization combining coupler 81. A polarization controller 72 for changing the branching ratio of the duplexed optical line is connected to the input port 71 side of the input polarization separation coupler 73. The polarization controller 72 changes the branching ratio of the duplex optical line so that the optical power is alternately conducted from the optical line without the fixed-length optical fiber 80.

  The continuous optical path length adjusting device is omitted, and a variable DGD generator 82 is disposed after the output polarization combining coupler 81. Each route of the duplex line is configured by a multistage connection system of optical switches 74 to 79 that can select two types of optical fibers having different lengths as the optical fiber switching device. The two types of optical fibers selected by the optical switches 74 to 79 have a difference in length proportional to a power of 2, and the shorter length is common to all the optical switches 74 to 79.

  Therefore, when the number of stages of the optical switch is N, the optical path length can be extended by L × 2 ^ N−1 for each unit length L by the combination of these ON / OFF. Such a system is advantageous to the optical fiber switching devices 17 and 19 in FIG. 1 in that the unit length L of the optical path length extension can be reduced with a limited number of optical switches. Since the fixed length optical fiber 80 of 1/2 unit length is further connected to the B route, the optical path length is changed by unit length (L) alternately from the A route by the ON / OFF operation of the optical switches 74 to 79. When increasing, the optical path length difference between both routes is always L / 2 (or -L / 2). Accordingly, since the optical signal synthesized by the output polarization synthesizing coupler 81 has a DGD corresponding to $ ± L / 2, this is compensated by the variable DGD generator 82.

It is assumed that the A route is separated and combined corresponding to the polarization x axis and the B route corresponding to the polarization y axis. When the optical path length of both routes is the shortest, the variable DGD generator 82 delays the phase of the x-axis by the amount corresponding to L / 2 with respect to the y-axis, so that the polarization controller 72 moves from the A route to the B route. In the meantime, the DGD of the output light from the variable DGD generator 82 is compensated. When light propagates only through the B route, if the optical path length is increased by L by the optical switch operation of the A route, a phase delay corresponding to L / 2 occurs with respect to the B route. Therefore, this time, if the variable DGD generator 82 is set so that the y-axis has a phase delay corresponding to L / 2 with respect to the x-axis, the DGD at the time of power transfer from the B route to the A route can be compensated. Become.
This method is also applicable to the configuration of FIG.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  DESCRIPTION OF SYMBOLS 11 ... Input port, 12 ... Polarization controller, 13 ... Polarization separation coupler, 14 ... 1st collimator, 15 ... 2nd collimator, 16 ... Mirror, 17 ... Optical fiber switching apparatus, 18 ... Polarization combining coupler, DESCRIPTION OF SYMBOLS 19 ... Optical fiber switching device, 20 ... Output port, 21 ... Continuous optical path length adjusting device, 22 ... Polarization maintaining optical fiber, 31 ... Input port, 32 ... Input polarization separation coupler, 33 ... Polarization controller, 34 ... Polarization separation coupler, 35... Polarization synthesis coupler, 36... First collimator, 37 .. mirror, 38... Second collimator, 39 .. optical fiber switching device, 40. , 42 ... Polarization controller, 43 ... Output polarization combining coupler, 44 ... Polarization controller, 45 ... Polarization separation coupler, 46 ... Polarization combining coupler, 47 ... Optical fiber switching device, 48 Polarization demultiplexing coupler, 49... Polarization combining coupler, 50... Polarization controller, 51... Output port, 52... Continuous optical path length adjusting device, 53. ... variable delay time adjustment device, 63, 64, 65, 66 ... optical fiber switching device, 71 ... input port, 72 ... polarization controller, 73 ... polarization separation coupler, 74 ... first optical switch, 75 ... second Optical switch, 76 ... third optical switch, 77 ... fourth optical switch, 78 ... fifth optical switch, 79 ... sixth optical switch, 80 ... fixed length optical fiber of 1/2 unit length , 81... Polarization combining coupler for output, 82... Variable DGD (differential group delay) generator, 83.

Claims (3)

A duplex optical line comprising a polarization maintaining optical fiber configured between a pair of input polarization separation couplers and an output polarization combining coupler;
Coupled to the two outputs of the polarization splitter coupler for input through a polarization controller that changes the branching ratio, respectively, the optical signals of the two optical lines are decomposed by the polarization splitter and the x-axis and y-axis respectively. A two-input two-output input side polarization demultiplexer that synthesizes the components alternately using a polarization coupler;
Coupled to the two inputs of the output polarization combining coupler via a polarization controller that changes the branching ratio, respectively, the optical signals of the two optical lines are decomposed by the polarization separation coupler and the x-axis and y-axis respectively. A two-input two-output output side polarization demultiplexer that synthesizes the components alternately using a polarization coupler;
An optical fiber switching device capable of changing the optical line length arranged in each of the duplex optical lines between the input side polarization beam splitter / combiner and the output side polarization beam splitter / combiner in a predetermined length step;
A continuous optical path length adjusting device capable of continuously adjusting the optical path length within a range including the predetermined length, provided in at least one of the duplex optical lines between the input side polarization splitter / combiner; An optical path length adjusting device for an optical line, comprising: In the optical path length adjusting device of the optical line according to claim 1 ,
An optical path length adjusting device for an optical line, wherein a continuous optical path length adjusting device is omitted and a variable DGD (differential group delay) generator is provided on the output port side of the output polarization combining coupler. Using the optical path length adjusting device for an optical line according to claim 2 ,
A first step of changing the branching ratio of the duplexed optical line by the polarization controller so that the optical power is conducted from one optical line to the other optical line;
A second step of increasing the unit length of the optical path in the optical fiber switching device in which the optical power of the duplexed optical line is not conducted;
A third step of inverting the polarity of the DGD corresponding to half the unit length with a variable DGD generator connected to the output polarization combining coupler of the duplexed optical line;
An optical path length adjustment method for an optical line, wherein the optical path length is extended by repeating the first step to the third step.

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