JP5650584B2 - Optical circuit, optical amplifier, tunable dispersion compensator, and variable optical delay device using the optical circuit - Google Patents

Description

  The present invention relates to an optical circuit used for an optical amplifier that amplifies signal light, an optical amplifier using the optical circuit, a tunable dispersion compensator, and a variable optical delay device.

  As communication traffic increases due to the rapid increase of video data such as video-on-demand, a wavelength division multiplexing (WDM) transmission system is commercially introduced to increase the transmission capacity per optical fiber. Yes. In a WDM transmission system, an optical amplifier has become an indispensable optical device for widening the band, reducing noise, and increasing output. In a WDM transmission system, the span loss fluctuates due to aging and temperature changes, so the signal light power input to the optical amplifier changes with time and temperature changes. It is necessary to output light. Conventionally, the optical amplifier is composed of two or more optical amplifying units and a variable optical attenuator, and the variable optical attenuator is arranged between the optical amplifying units to adjust the attenuation amount of the variable optical attenuator. Thus, an optical amplifier that compensates for fluctuations in the input signal light power has been used (for example, Patent Document 1).

Japanese Patent No. 3298396

Y. Sun et al, "Averaging Inversion level, modeling, and physicals of berbium-doped fiber amplifier," IEEE Journal of Selected Quantum in Quantum in Quant. 3, no. 4, pp. 991-1007, 1997.

  However, in the optical amplifier of the conventional configuration, after the signal light is once amplified by the optical amplification unit in the previous stage, the signal optical power is attenuated by the variable optical attenuator between the optical amplification units. A part of the pumping light power used for amplification in wasted. This is particularly noticeable at high input signal light power where the attenuation of the variable optical attenuator is large.

  In addition, if the power range (input dynamic range) of the signal light input to the optical amplification unit at the subsequent stage is large, the amount of attenuation of the variable optical attenuator is set to be larger in accordance with the larger input power. As a result of the significant reduction in power, the contribution of noise components added in the subsequent optical amplifying section increases, leading to degradation of the noise characteristics of the entire optical amplifier (increase in noise figure). Therefore, in order to avoid such disadvantages of the optical amplifier in system operation, an optical amplifier that requires a large input dynamic range divides the input signal light power range into a plurality of small ranges, and each input signal light It is necessary to use different optical amplifiers in the power range. When the system operation is performed so that a plurality of optical amplifiers are used properly, there is a disadvantage that the system operation cost is increased, for example, it is necessary to have a plurality of spare optical amplifiers for replacement at the time of failure.

  Furthermore, depending on the optical amplifying medium of the optical amplifier, the gain spectrum has pumping light power dependency (that is, inversion distribution state dependency). Therefore, when the gain is adjusted by the pumping light power, the gain due to the wavelength channel in wavelength multiplexing transmission There also arises a problem that a deviation occurs.

  The present invention has been made in view of the above circumstances, and does not waste pump light power, but compensates for fluctuations in input signal light power and outputs signal light at a constant light power level (light power per wavelength is constant). And an optical circuit for realizing an optical amplifier capable of avoiding an increase in noise and a decrease in efficiency which have occurred in a conventional optical amplifier when the input signal optical power dynamic range is wide, and an optical amplifier using this optical circuit. It is to provide. Furthermore, a tunable dispersion compensator and a tunable optical delay device using the circuit of the present invention are provided.

  The present invention has been made to solve the above problems. The optical circuit of the present invention includes one main input port, N sub input ports, one 1 × N main optical switch, one N × 1 main optical switch, and 1 × j sub light. N−1 1 × j slave optical switches in which j is an integer of 2 to N, and i × 1 slave switches, where i is an integer of 2 to N. It is composed of one i × 1 slave optical switch, N slave output ports, and one master output port. The master input port is connected to the input port of the 1 × N master optical switch. Of the N slave input ports, each of the N−1 slave input ports is connected to each input port of the N−1 1 × j slave optical switch, and N−1 1 × j. Of the N slave input ports not connected to the input port of the slave optical switch, one slave input port is N of the N × 1 master optical switch. It is connected to one of the input ports, the main output port is connected to the output port of the N × 1 main optical switch, and N−1 subordinate output ports of the N subordinate output ports. Each of the output ports is connected to a respective output port of the N−1 i × 1 slave optical switch and is connected to the output port of the N−1 i × 1 slave optical switch. One slave output port of the slave output ports is connected to one output port of N output ports of the 1 × N master optical switch, and N−1 1 × j slave lights. One of the output ports of each 1 × j slave optical switch of the switch is not connected to one slave input port of the N input ports of the N × 1 master optical switch. Connected to each of the N-1 input terminals of the switch, 1 × N main optical switch N−1 output ports of the 1 × N master optical switch that are not connected to one slave output port among the N output ports of the H are N−1 i × 1 slave switch respectively. Of the Nth 1 × j subordinate optical switch and not connected to the input port of the N × 1 main optical switch among the output ports of the kth 1 × j subordinate optical switch. Each of the j−1 output ports is not connected to the output port of the 1 × N master optical switch among the input ports of the l-th i × 1 slave switch of the N−1 i × 1 slave optical switch. Each of the i−1 input ports is connected so as to satisfy the condition that l is an integer equal to or larger than k, and 1 × N master optical switch and / or N−1 1 × j slave optical switch By switching, one master input port, N slave input ports, and N slave input ports Characterized in that it is possible to switch and power port, a combination of the connection between the one of the main output port.

  Further, a variable optical attenuator is provided before or after N−1 i × 1 subordinate optical switches or after N−1 1 × j subordinate optical switches.

  Further, dynamic gain equalization means for making the difference between the peak and dip of the loss spectrum variable before or after N−1 i × 1 subordinate optical switches or after N−1 1 × j subordinate optical switches. It is characterized by providing.

  Further, a 1 × N master optical switch, an N × 1 master optical switch, N−1 i × 1 slave optical switches, N−1 1 × j slave optical switches, a variable optical attenuator, At least two of the dynamic gain equalization means are integrated in a single waveguide substrate.

  The optical amplifier according to the present invention further includes N optical amplifying optical fibers, and the N slave output ports are connected to the input ports of the N optical amplifying optical fibers, respectively. The output port of the optical amplification optical fiber connected to one slave output port of the amplification optical fiber is 1 × j slave light satisfying j = N among N−1 1 × j slave optical switches. I × 1 sub-optical switch connected to a sub input port connected to the switch and satisfying i = N among N−1 i × 1 sub-optical switches of N optical amplifying optical fibers The output port of the optical amplifying optical fiber connected to the slave output port connected to is connected to one slave input port, and the N-1 optical fibers among the N optical amplifying optical fibers are connected. The N-1 slaves connected to each of the output ports of the i × 1 slave switch The output port of the optical amplifying optical fiber connected to the power port has the N− connected to each of the output ports of the N−1 1 × j sub optical switches so that j = N−i + 1 is satisfied. Optical amplification by switching the combination of optical fibers for optical amplification by switching the 1 × N master optical switch and / or the N−1 1 × j slave optical switch connected to one slave input port It is characterized in that the length of the optical fiber for use can be changed, and thus the optical gain can be changed.

  The tunable dispersion compensator of the present invention can be obtained by replacing the optical amplifying optical fiber of the optical amplifier of the present invention with a dispersion compensating fiber, and 1 × N main optical switch and / or N−1 1 × j The length of the dispersion compensation fiber can be changed by changing the combination of the dispersion compensation fibers by changing the slave optical switch, and the dispersion compensation amount can be changed accordingly.

  The variable optical delay device of the present invention can be obtained by replacing the optical amplification optical fiber of the optical amplifier of the present invention with an optical delay waveguide, and 1 × N main optical switch and / or N−1 1 × The feature of the present invention is that the length of the optical delay waveguide can be changed by changing the combination of the optical delay waveguides by switching the j slave switch, thereby changing the optical delay amount.

  In the optical amplifier using the optical circuit of the present invention, the combination of the amplification optical fibers can be changed by switching the optical switch. As a result, the total length of the amplification optical fibers through which the signal light passes changes. Variable gain is obtained. The optical amplifier of the present invention switches the combination of amplification optical fibers in response to changes in the input signal light power and always performs optical amplification with an amplification optical fiber of an appropriate length, so that it has a wide input signal light power dynamic range. There is an advantage that it is possible to avoid an increase in noise and a decrease in efficiency which have occurred in the conventional optical amplifier when the pumping light power is not wasted and the input signal light power dynamic range is wide. This advantage also has the advantage that it is not necessary to use a plurality of optical amplifiers separately in system operation.

  In this technology, the gain of the amplification optical fiber is adjusted not by the pumping light power but by the length of the amplification optical fiber, so that the gain spectrum of the amplification optical fiber is constant regardless of the gain, and in wavelength multiplexing transmission. The problem that the gain deviation between wavelength channels changes can be avoided.

  Further, with respect to the tunable dispersion compensator and the variable optical delay device using the circuit of the present invention, the same effects as those of the optical amplifier using the optical circuit of the present invention can be obtained.

It is a conceptual diagram for demonstrating the effect | action of this invention. 1 is a block diagram illustrating an optical circuit according to a first embodiment of the present invention. An example of the amplification block of the present invention is shown, (a) is a forward excitation system, (b) is a backward excitation system, (c) is a bidirectional excitation system, (d) is an optical isolator arranged in FIG. (E) is an optical isolator arranged in FIG. 3 (b), (f) is an optical isolator arranged in FIG. 3 (c), and (g) is a block showing an amplification block in which an optical isolator is arranged between optical fibers for amplification. FIG. It is a conceptual diagram explaining that an optical circuit and an amplification block are connected by a fiber block. It is a block diagram which shows the example of the optical circuit in the 1st Embodiment of this invention. It is a block diagram which shows the example of the optical circuit in the 1st Embodiment of this invention. It is a block diagram which shows the example of the optical circuit in the 1st Embodiment of this invention. It is a block diagram which shows the example of the optical circuit in the 1st Embodiment of this invention. It is a block diagram which shows the optical circuit in the 2nd Embodiment of this invention. It is a conceptual diagram explaining that an optical circuit and an optical fiber for amplification are connected by a fiber block. It is a block diagram which shows the optical circuit in the 2nd Embodiment of this invention. It is a block diagram which shows the 3rd Embodiment of this invention. It is a block diagram which shows the optical amplifier in the 4th Embodiment of this invention. It is a figure which shows the optical circuit structure in the 4th Embodiment of this invention. (A) is a level diagram of an optical amplifier according to a fourth embodiment of the present invention, and (b) is a diagram showing a level diagram of a conventional optical amplifier. It is a figure which compares the required excitation light power of the optical amplifier of the 4th Embodiment of this invention, and the conventional optical amplifier. It is a figure which compares the noise figure of the optical amplifier of the 4th Embodiment of this invention, and the conventional optical amplifier. It is a block diagram which shows the optical amplifier in 5th Embodiment.

  The optical circuit of the present invention connects two or more amplification optical fibers, changes the combination of the amplification optical fibers by switching the optical switch, and sets the total length of the amplification optical fibers through which the signal light passes. The main feature is to change.

<Action>
The function of the optical circuit and optical amplifier of the present invention will be described with reference to the conceptual diagram shown in FIG. In FIG. 1, the optical circuit of the present invention includes a 1 × N optical switch 901, an N × 1 optical switch 902, and N−1 i × 1 optical switches 903-1 to 903- (N−1), where i is An integer of 2 to N and N−1 1 × j optical switches 904-1 to 904- (N−1), where j is an integer of 2 to N. When the optical circuit of the present invention further includes N + 1 amplification blocks k905-0 to 905-N each having an optical fiber for amplification, where k is an integer of 0 to N, the optical circuit of the present invention has a plurality of The optical amplifier is composed of an optical switch and a plurality of amplification blocks.

  The input port of the 1 × N optical switch is connected to the output port of the amplification block 0. One of the N output ports of the 1 × N optical switch is connected to the amplification block 1. Of the N output ports of the 1 × N optical switch, N−1 output ports that are not connected to the amplification block 1 are connected to respective input ports of the N−1 i × 1 optical switches. Yes. The output port of the amplification block k in which k is 1 or more and N−1 or less is connected to the input ports of N−1 1 × j optical switches so as to satisfy j = N−k + 1. The output port of the amplification block N is connected to the input port of the N × 1 optical switch. One of the output ports of the 1 × j optical switch is connected to the input port of the N × 1 optical switch that is not connected to the output port of the amplification block N. Of the output ports of the 1 × j optical switch, the output ports that are not connected to the input port of the N × 1 optical switch are connected to the output port of the 1 × N optical switch where i satisfies N−j + 2 or more and N or less, respectively. The i × 1 optical switch that was not connected is connected to each input port. The output port of the i × 1 optical switch is connected to the input port of the amplification block k where i = k.

  The input signal light is amplified by the amplification block 0 and then input to the optical switch 901 that is a 1 × N switch, and the signal light is directed to one of N paths from the output port of the optical switch 901. The signal light that has passed through the optical switch 901 is input to the amplification block k via the amplification block 1 or the i × 1 optical switches 903-1 to 903- (N−1). The optical signal amplified by the amplification block k is input to the 1 × j optical switch connected to the amplification block k, or to the N × 1 optical switch 902 when k = N. The optical signal input to the 1 × j optical switch is directed to one of the paths from the j output ports, and input to the i × 1 optical switch connected to the 1 × j optical switch or the N × 1 optical switch. Is done. As described above, the signal light is amplified by a combination of the optical switches 903-1 to 903- (N-1), the amplification blocks 905-1 to 905-N, and the optical switches 904-1 to 904- (N-1). After being repeated one or more times, the light finally passes through the optical switch 902 and is output. The configuration of FIG. 1 may be configured such that when the loss of the optical switch 901 is not a problem, the amplification unit 0 is eliminated and an input signal is directly input to the optical switch 901.

  In this way, the signal light passes through the path switching of the 1 × N optical switch 901, the N × 1 optical switch 902, the N−1 i × 1 optical switches, and the N−1 1 × j optical switches. The total length of the amplification optical fibers through which the signal light passes is changed by changing the combination of the amplification blocks (that is, the amplification optical fibers), that is, by switching the optical switch and changing the path of the signal light. At that time, when the amplification optical fiber is an erbium-doped fiber, as shown in Non-Patent Document 1, the gain obtained by the amplification optical fiber is proportional to the unit length. The gain of the optical amplifier can be changed by changing the total length of the optical fiber.

<Embodiment of the Invention>
(First embodiment)
FIG. 2 is a block diagram showing an optical circuit according to the first embodiment of the present invention. In FIG. 2, the optical circuit of the present embodiment includes one main input port, N sub input ports 1 where l is an integer of 1 to N, one 1 × N optical switch, 1 N × 1 optical switches, N−1 1 × j optical switches where j is an integer between 2 and N, and N−1 i × 1 lights where i is an integer between 2 and N The switch is composed of N sub-output ports m in which m is an integer of 1 to N and one main output port.

  The main input port is connected to the input port of the 1 × N optical switch. Of the N slave input ports, each of the N−1 slave input ports is connected to each input port of the N−1 1 × j optical switch, and N−1 1 × j optical ports. The slave input port that is not connected to the input port of the switch is connected to one of the N input ports of the N × 1 optical switch. The main output port is connected to the output port of the N × 1 optical switch. Of the N slave output ports, each of the N-1 slave output ports is connected to each output port of the N-1 i × 1 optical switch, and N−1 i × 1 optical ports are connected. The slave output port that is not connected to the output port of the switch is connected to one output port among the N output ports of the 1 × N optical switch. One of the output ports of each 1 × j optical switch of the N−1 1 × j optical switches is connected to one slave input port of the N input ports of the N × 1 optical switch. It was connected to each of the N-1 input terminals that did not exist. N−1 output ports of the 1 × N optical switch that are not connected to one of the N output ports of the N output ports of the 1 × N optical switch are N−1 i × 1 optical switches. Connected to each input port. Out of the output ports of the 1 × j optical switches of the N−1 1 × j optical switches, each of the output ports not connected to the input port of the N × 1 optical switch is N−1 i × 1. Of the input ports of the optical switch, each input port that is not connected to the output port of the 1 × N main optical switch is connected so as to satisfy the condition that i is an integer not smaller than N−j + 2 and not larger than N. When the output of the amplification block 0 is connected to the main input port, the input port of the amplification block 1 is connected to the slave output port 1, and the input port 1 is connected to the output port of the amplification block 1, the configuration shown in FIG.

  FIG. 3 shows an example of the amplification block, and each is composed of an amplification optical fiber 11 and a multiplexer / demultiplexer 12 that combines the signal light and the pumping light. 3A shows a forward excitation system, FIG. 3B shows a backward excitation system, and FIG. 3C shows a bidirectional excitation system. Although not shown, one port of the multiplexer / demultiplexer is connected to a pumping light source (for example, a semiconductor laser) that generates pumping light and an optical branching device that branches the pumping light into a plurality of ports. Further, if necessary, an optical isolator 13 may be disposed (for example, FIGS. 3D, 3E, and 3F), and a plurality of amplification optical fibers may be provided, and the optical isolator is interposed between the amplification optical fibers. 13 or a gain equalizing filter may be arranged (for example, FIG. 3G).

  As shown in the conceptual diagram of FIG. 4, the optical circuit and the amplification block are connected by fixing one end of the N + 1 fibers 21 with the V-groove glass block 20 and polishing the end face on the same plane as the fiber end face. Connected through a fiber block. The connection end faces of the fiber block and the optical circuit are polished at an angle of 7 degrees or more with respect to a plane perpendicular to the optical axis. The other unpolished side of each fiber of the fiber block and the pigtail fiber of the amplification block are fusion spliced.

  Hereinafter, the operation of the optical circuit of this embodiment will be described on the assumption that an amplification block is connected to the slave output port, slave input port, and master input port of FIG. The signal light is amplified by the amplification block 0 and then input to the 1 × N optical switch 1 and is directed to any one of N paths at the output port of the 1 × N optical switch 1. The signal light is amplified by the previous amplification block to which the signal light is directed and then amplified by the next amplification block that is directed by the optical switch, and this process is repeated. The signal light passes through the amplification optical fiber length having a desired gain, and then passes through the N × 1 optical switch 2 and is output. At this time, a desired variable gain can be obtained by changing the total length of the amplification optical fiber by switching the optical switch in accordance with the use conditions, for example, the input signal light power and the environmental temperature.

  An example of another optical circuit in the present embodiment will be described below. FIG. 5 shows an optical circuit provided with a variable optical attenuator 5 in the optical circuit of FIG. In the optical circuit of FIG. 2, the gain of the optical amplifier changes discretely in gain units depending on the length of the amplification optical fiber of each amplification block. For this reason, a continuous variable gain cannot be obtained with this optical amplifier. On the other hand, in the optical circuit of FIG. 5, by adjusting the attenuation amount of the variable optical attenuator of the amplification block, it is possible to interpolate between gains that change discretely in gain units depending on the length of the optical fiber for amplification. Continuously variable gain can be obtained. Thus, the variable optical attenuator may be integrated in the switch.

  6 and 7 show an optical circuit provided with a variable optical attenuator for each amplification block instead of one variable optical attenuator. In the optical circuit of FIG. 5, since the discrete gain is interpolated by the attenuation amount of one variable optical attenuator in gain units depending on the length of the amplification optical fiber of each amplification block, the variable optical attenuator is The attenuation of the signal light power after passing increases, and as a result, the noise characteristic of the optical amplifier tends to deteriorate (the noise figure tends to increase). On the other hand, in the optical circuits of FIG. 6 and FIG. 7, in order to perform interpolation between discrete gains in gain units depending on the length of the amplification optical fiber of each amplification block by adjusting the attenuation amounts of a plurality of variable optical attenuators, Since the attenuation of the signal light power after passing through the variable optical attenuator is smaller than that in the case of the optical circuit of FIG. 5 and the signal light power is kept at a high level, an increase in the noise figure of the optical amplifier can be suppressed.

  FIG. 8 shows an optical circuit provided with a dynamic gain equalizer 6 in the optical circuit of FIG. In the optical amplifier using the optical circuit shown in FIGS. 2 to 7, if the amplification block is not equipped with a dynamic gain equalizer, when the total length of the amplification optical fiber is changed by switching the optical switch, The gain difference between the peak and the dip generated in the gain spectrum changes. For this reason, the difference (gain deviation) between the maximum value and the minimum value of the gain within the desired band is changed by switching the optical switch. On the other hand, in the optical circuit of FIG. 8, the gain deviation is constant even when the total length of the amplification optical fiber is changed by switching the optical switch by changing the spectrum of the equalization filter with a dynamic gain equalizer. Can keep. Here, FIG. 8 shows an optical circuit provided with only one dynamic gain equalizer, but the same effect can be obtained with an optical circuit provided with a gain equalizer for each amplification block as well as a variable optical attenuator. Is obtained.

  The shape and arrangement of the optical waveguide in this optical circuit are not necessarily the same as those shown in FIGS. 2 to 8 if the connections of the optical switch, variable optical attenuator, and dynamic gain equalizer are as described above. Need not be.

(Second Embodiment)
FIG. 9 is a block diagram showing an optical circuit according to the second embodiment of the present invention. The optical circuit shown in FIG. 9 combines / demultiplexes the signal light and the excitation light in FIG. 3A when the amplification block shown in FIG. 3A is connected to the optical circuit shown in FIG. The device is incorporated in the optical circuit of the present invention.

  As shown in the conceptual diagram of FIG. 10, the optical circuit of this embodiment is connected to the amplification optical fiber by fixing one end of the N + 1 fibers 121 with the V-groove glass block 120 and the same as the end face of the fiber. The end faces on the surface are connected via a polished fiber block. The connection end faces of the fiber block and the optical circuit are polished at an angle of 7 degrees or more with respect to a plane perpendicular to the optical axis. The other unpolished side of each fiber of the fiber block and the pigtail fiber of the amplification block are fusion spliced.

  The function of the optical circuit of the present embodiment is to change the total length of the amplification optical fiber by switching the optical switch according to the use conditions, for example, the input signal light power and the environmental temperature, as in the first embodiment. Thus, a variable gain can be obtained. In the optical circuit of FIG. 9, a multiplexer / demultiplexer that multiplexes signal light and pumping light is disposed only on the input side of each amplification optical fiber (forward pumping system). However, as shown in FIG. In some cases, an optical circuit in which multiplexers / demultiplexers are arranged at both ends of the optical fiber is better. The optical circuit shown in FIG. 11 combines / demultiplexes the signal light and the excitation light in FIG. 3C when the amplification block shown in FIG. 3C is connected to the optical circuit shown in FIG. Is incorporated into the optical circuit of the present invention. For example, when the total pumping light power is not sufficient only by forward pumping, the configuration of bidirectional pumping light in which pumping light is input from both the input and output sides of the amplification optical fiber is taken using the optical circuit configuration of FIG. Alternatively, if there is residual pumping light that passes through the amplification optical fiber even when only the forward pumping light is input to the amplification fiber, the multiplexer / demultiplexer on the amplification fiber output side is used by using the optical circuit configuration of FIG. By terminating the pumping light port, the residual pumping light can be prevented from being reflected and returned to the amplification optical fiber, and stable amplification can be obtained.

  In the optical circuit shown in the present embodiment, a continuously variable gain is obtained using a variable optical attenuator or a dynamic gain equalizer as shown in FIGS. 5 to 8 in the first embodiment. It is apparent from the similarity between the first embodiment and the present embodiment that the gain deviation can be kept constant. In addition, the shape and arrangement of the optical waveguide in this optical circuit is the same as described above for the optical switch, multiplexer / demultiplexer, and connection (variable optical attenuator arranged as necessary, dynamic gain equalization The same applies to the container), and it is not necessarily required to be as shown in FIGS.

(Third embodiment)
FIG. 12 is a block diagram showing a third embodiment of the present invention. In FIG. 12, the optical circuit of this embodiment includes a 1 × N optical switch 201, an N × 1 optical switch 202, N−1 2 × 1 optical switches 204-1 to 204- (N−1), N−. One 1 × 2 optical switch 203-1 to 203- (N−1) and N + 1 amplification blocks k, where k is an integer from 0 to N.

  An amplification block 0 is connected to the input port of the optical switch 201. The amplification block 1 is connected to one of the N output ports of the N × 1 optical switch 201, and the other N−1 output ports of the N × 1 switch 201 are respectively 2 × 1 optical switch 204-1. To 204- (N-1) input ports. The input ports of the amplification block 2 to the amplification block N are connected to the output ports of the N−1 2 × 1 optical switches 204-1 to 204- (N−1), respectively. The output ports of the amplification block 1 to the amplification block N-1 are connected to the input ports of N−1 1 × 2 optical switches 203-1 to 203- (N−1), respectively. The output port of the amplification block N and the output ports of the N−1 1 × 2 optical switches 203-1 to 203- (N−1) are connected to the input port of the N × 1 optical switch 202.

  The configuration of each amplification block is the same as that shown in FIG. One port of the multiplexer / demultiplexer is connected to an excitation light source (for example, a semiconductor laser) that generates excitation light and an optical branching device that branches the excitation light into a plurality of ports. In addition, an optical isolator may be arranged as necessary, or a plurality of amplification optical fibers may be used, and an optical isolator or a gain equalization filter may be arranged between the amplification optical fibers. It is the same.

  The connection between the optical circuit and the amplification block is the same as the conceptual diagram in FIG. 4, and one end of N + 1 fibers is fixed with a V-groove glass block, and the end face on the same plane as the end face of the fiber is polished. Connected through. The connection end faces of the fiber block and the optical circuit are polished at an angle of 7 degrees or more with respect to a plane perpendicular to the optical axis. The other unpolished side of each fiber of the fiber block and the pigtail fiber of the amplification block are fusion spliced.

  The signal light is amplified by the amplification block 0 and then directed to one of N paths at the output port of the 1 × N optical switch 1. The signal light is amplified by the previous amplification block to which the signal light is directed and then amplified by the next amplification block that is directed by the optical switch, and this process is repeated. The signal light passes through the amplification optical fiber length having a desired gain, and then passes through the N × 1 optical switch and is output. At this time, a variable gain can be obtained by changing the total length of the amplification optical fiber by switching the optical switch in accordance with the use conditions, for example, the input signal light power and the environmental temperature.

  In the optical circuit shown in the present embodiment, a continuously variable gain is obtained using a variable optical attenuator or a dynamic gain equalizer as shown in FIGS. 5 to 8 in the first embodiment. It is apparent from the similarity between the first embodiment and the present embodiment that the gain deviation can be kept constant. In addition, the shape and arrangement of the optical waveguide in this optical circuit is the same as described above for the optical switch, multiplexer / demultiplexer, and connection (variable optical attenuator arranged as necessary, dynamic gain equalization The same applies to the container), and it is not necessarily required to be as shown in FIGS.

(Fourth embodiment)
FIG. 13 is a block diagram showing an optical circuit and an optical amplifier using the same according to the fourth embodiment of the present invention. In FIG. 13, the optical circuit of the present embodiment includes a 1 × 3 optical switch 301, a 3 × 1 optical switch 302, a 2 × 1 optical switch 303-1, a 3 × 1 optical switch 303-2, and a 1 × 3 optical switch 304. -1, 1 × 2 optical switch 304-2, variable optical attenuators 305-1 to 305-6, multiplexers / demultiplexers 306-1 to 306-8 for multiplexing signal light and pumping light (used as demultiplexers) And the dynamic gain equalizer 340 is formed on the planar lightwave circuit 300. Further, the planar lightwave circuit 300 includes a signal input waveguide 351-1, signal input waveguides 351-2 to 351-5, signal output waveguides 352-1 to 352-5, and excitation light input waveguides 361-1 to 361-1. 361-4, excitation light output waveguides 361-5 to 361-8, amplification optical fibers 320-0 to 320-3, and optical isolators 330-1 to 330-2 are connected. In this embodiment, an erbium-doped fiber is used as the amplification optical fiber. The connection relationship between each element is as follows.

Common port for signal input waveguide 351-2 and multiplexer / demultiplexer 306-5 (input / output ports for combined signal light and pump light)
Common port for signal input waveguide 351-3 and multiplexer / demultiplexer 306-6 Common port for signal input waveguide 351-4 and multiplexer / demultiplexer 306-7 Signal input waveguide 351-5 and multiplexer / demultiplexer 306- 8 common ports signal optical port of multiplexer / demultiplexer 306-5 and input port of dynamic gain equalizer 340 signal optical port of multiplexer / demultiplexer 306-6 and input port of 1 × 2 optical switch 304-1 ( 16)
Signal optical port of multiplexer / demultiplexer 306-7 and input port (20) of 1 × 2 optical switch 304-2
Signal optical port of multiplexer / demultiplexer 306-8 and input port (14) of 3 × 1 optical switch 302
Output port of dynamic gain equalizer 340 and input port (1) of 1 × 3 optical switch 301
Output port (2) of 1 × 3 optical switch 301 and input port of variable optical attenuator 305-1 Output port (3) of 1 × 3 optical switch 301 and input port of variable optical attenuator 305-2 1 × 3 light Output port (4) of switch 301 and input port of variable optical attenuator 305-4 Output port (17) of 1 × 3 optical switch 304-1 and input port of variable optical attenuator 305-3 1 × 3 optical switch 304 -1 output port (18) and variable optical attenuator 305-5 input port 1 × 3 optical switch 304-1 output port (19) and 3 × 1 optical switch 302 input port (12)
Output port (21) of 1 × 2 optical switch 304-2 and input port of variable optical attenuator 305-6 Output port (22) of 1 × 2 optical switch 304-2 and input port of 3 × 1 optical switch 302 ( 13)
Output port of variable optical attenuator 305-1 and signal port of multiplexer / demultiplexer 306-2 Output port of variable optical attenuator 305-2 and input port of 2 × 1 optical switch 303-1 (5)
Output port of variable optical attenuator 305-3 and input port of 2 × 1 optical switch 303-1 (6)
Output port of variable optical attenuator 305-4 and input port of 3 × 1 optical switch 303-2 (8)
Output port of variable optical attenuator 305-5 and input port of 3 × 1 optical switch 303-2 (9)
Output port of variable optical attenuator 305-6 and input port of 3 × 1 optical switch 303-2 (10)
Output port (7) of 2 × 1 optical switch 303-1 and signal port of multiplexer / demultiplexer 306-3 Output port (11) of 3 × 1 optical switch 303-2 and signal port of multiplexer / demultiplexer 306-4 Output port (15) of 3 × 1 optical switch 302 and signal output waveguide 352-5
Common port of multiplexer / demultiplexer 306-1 and signal output waveguide 352-1
Common port of multiplexer / demultiplexer 306-2 and signal output waveguide 352-2
Common port of multiplexer / demultiplexer 306-3 and signal output waveguide 352-3
Common port of multiplexer / demultiplexer 306-4 and signal output waveguide 352-4
Excitation light ports of pumping light input waveguides 361-1 to 361-4 and multiplexers / demultiplexers 306-1 to 306-4 Pumping light output waveguides 361-5 to 361-8 and multiplexer / demultiplexers 306-1 ~ 306-4 excitation light port

  Each input / output waveguide of the planar lightwave circuit is connected to erbium-doped fibers 320-0 to 320-3 by a fiber block in which a plurality of optical fibers are fixed by V-groove glass blocks (310-1 and 310-2). Yes. In this embodiment, a fiber block in which an amplification optical fiber (erbium-doped fiber in this embodiment) is fixed to a V-groove glass block is used. However, a fiber block in which a single mode fiber having no amplification action is fixed to a V-groove glass block. Even if the single mode fiber and the amplification optical fiber are fused and connected, there is a disadvantage that the workability on the mounting surface is reduced at the fusion splicing point, but the amplification characteristic can be used without any problem. The connection relationship between the input / output waveguides of the planar lightwave circuit and the erbium-doped fiber is as follows.

Input of signal output waveguide 352-1 and erbium-doped fiber 320-0 Input of signal output waveguide 352-2 and erbium-doped fiber 320-1 Input of signal output waveguide 352-3 and erbium-doped fiber 320-2 Input of waveguide 352-4 and erbium doped fiber 320-3

  Further, an optical isolator 330-1 is connected to the signal input waveguide 351-1 of the planar lightwave circuit, and an optical isolator 330-2 is connected to the output waveguide 352-5.

  Although the pumping light source is not shown, the optical amplifier is equipped with at least one pumping light source, and the pumping light source is connected to the multiplexer / demultiplexer.

  FIG. 14 shows a circuit configuration of the planar lightwave circuit 300 shown in FIG. The elements represented by the respective reference numerals in FIG. 14 correspond to the elements represented by the same reference numerals in FIG. All the elements represented by the double line squares in FIG. 14 represent an asymmetric Mach-Zehnder interferometer (MZI). Dotted lines enclosing the squares of the double lines represent the respective optical switches and variable optical attenuators, and are incomplete 4 × 4 switches having waveguides through which signal light does not propagate. Each optical switch and variable optical attenuator are manufactured by using MZIs having different optical path difference lengths of two arms as unit elements, and each path switched by the optical switch passes through two or more MZIs. As a result, crosstalk due to leaked light in the MZI is sufficiently reduced. The optical switch and the variable optical attenuator do not have the MZI independently, but a part of the MZI constituting the optical switch operates as a variable optical attenuator. The signal light propagates from the left side to the right side of the portion surrounded by the dotted line in the MZI constituting each optical switch and the variable optical attenuator, and the amplification optical fiber m (m = 0, 1, 2, 3) 320-0. The signal light propagates from 320-3 to the amplification optical fiber n (n = 1, 2, 3) 320-1 to 320-3 or the signal output. Symbols mnA, mnB, and nmC described in the squares of the double lines representing each MZI are from the amplification optical fiber m to the amplification optical fiber n (for convenience, n = S is set for signal output). When propagating, this means that the heater power associated with MZI of mnA, mnB, and nmC is turned on.

  Each of the multiplexers / demultiplexers 306-1 to 306-8 is composed of two MZIs, and combines the 980 nm band excitation light and the C band signal light (that is, the wavelength of 1530-1565 nm), and C The optical path length is adjusted so that the transmission spectrum of the band is flat. The dynamic gain equalizer has a configuration in which a dielectric multilayer film is inserted into one arm of the MZI. With this configuration, it is possible to make the MZI branching ratio variable (by shifting the phase with a heater attached to the other arm, making the optical path length difference variable, making the branching ratio variable), and gain. While maintaining the spectrum shape of the equalization filter, that is, without changing the wavelength dependence of the filter loss, the loss amount of each wavelength can be increased or decreased, and the difference between the gain peak and dip difference due to the total length change of the erbium-doped fiber Changes can be compensated.

  In this embodiment, the fiber lengths of the erbium-doped fibers 320-0, 1, 2, and 3 are 5.4 m, 3.6 m, 5.4 m, and 1.8 m, respectively, and the average gain is 9.0 dB and 6 m, respectively. 0.0 dB, 9.0 dB, and 3.0 dB, and the variable gain range is 9.0 to 27.0 dB. As shown in Table 1, there are six optical amplifier gain and erbium-doped fiber combination patterns, and the optical switch is switched so as to obtain a suitable erbium-doped fiber combination according to the input signal light power.

FIG. 15 shows an optical amplifier internal level diagram of the present invention. The level diagram of this embodiment is shown in FIG. 15A, and the level diagram of the conventional optical amplifier is shown in FIG. 15B. The input signal light power per wave (that is, per channel) is −25 to −7 dBm / ch, the maximum gain G _max = 27 dB, and the minimum G _mim = 9 dB. As can be seen from FIG. 15, in the optical circuit of this embodiment, the discrete gain difference caused by the gain switching by the optical switch is 3 dB. Therefore, the attenuation amount of the variable optical attenuator is 3 dB at the maximum, and the signal light power Is suppressed to be small. However, in FIG. 15, the transmission loss and dynamic gain equalizer of each optical switch and waveguide are sufficiently below 0.1 dB, so that the transmission loss and dynamic gain of each optical switch and waveguide are equalized. Since the influence of the excess loss of the device is negligible, the propagation of these elements is omitted. On the other hand, in the conventional optical amplifier, the maximum attenuation of the variable optical attenuator is 18 dB, and the attenuation of the signal light power is increased. For this reason, the required pumping light power increases and the noise figure increases significantly.

  FIG. 16 shows the optical amplifier gain dependence of the required pumping light power of the optical amplifier of this embodiment and the conventional optical amplifier. In the optical amplifier according to the present embodiment, the required pumping light power increases when the gain is large, but when the gain is small, the required pumping light power decreases by about 10% as compared with the conventional optical amplifier. In addition, the maximum required pumping light power of the present embodiment is smaller than that of the conventional optical amplifier, and the output light power class of the pumping light source mounted in the optical amplifier can be smaller than that of the conventional optical amplifier, and the required pumping power is required as compared with the conventional optical amplifier. It can be seen that the optical power can be reduced.

  FIG. 17 shows the noise figure of the optical amplifier of this embodiment and the conventional optical amplifier. In the conventional optical amplifier, the attenuation of the variable optical attenuator increases as the optical amplifier gain decreases, and the noise figure increases accordingly. On the other hand, in the optical amplifier of the present embodiment, as the gain of the optical amplifier decreases, the gain in one erbium-doped fiber combination pattern has a maximum attenuation of the variable optical attenuator, so that the noise figure is 0.5 dB. Although the degree of increase increases, the noise figure returns to the minimum value when the optical switch is switched and the erbium-doped fiber combination pattern is different, and the noise figure can be greatly reduced as compared with the conventional optical amplifier.

  When the optical amplifier according to the present embodiment is operated in an optical transmission system, it is necessary to avoid a transmission error at the switching time of the optical switch when the range of the input signal optical power fluctuation includes the input signal optical power that switches the optical switch. Sometimes there are. In that case, the optical switch may not be switched before and after the input signal light power at which the optical switch is switched, and the gain may be made variable by the attenuation amount of the variable optical attenuator. In this case, the maximum attenuation of the variable optical attenuator becomes larger than the above-mentioned 3 dB, but the change factor of the input signal light power in this case is mainly the transmission fiber loss due to aging and temperature change, and the input signal light power Since the change in is about 1 to 2 dB at most, the maximum attenuation of the variable optical attenuator is 4 to 5 dB, and the influence on the increase in the noise figure is small, which is not a problem.

(Fifth embodiment)
FIG. 18 is a block diagram showing an optical circuit and an optical amplifier using the same according to the fifth embodiment of the present invention. The optical circuit of the present embodiment is similar to the optical circuit of the fourth embodiment, but among the elements in the optical circuit of the fourth embodiment, the optical switch 303-2 is changed from the 3 × 1 optical switch to the 2 ×. The optical switch 304-1 is different from the 1 × 3 optical switch to the 1 × 2 optical switch. Thus, even if the number of ports of a specific optical switch is reduced, the optical amplifier using the optical circuit of the present embodiment realizes exactly the same erbium-doped fiber combination pattern as the optical amplifier using the optical circuit of the fourth embodiment. can do.

  Therefore, it can be seen that i and j of the i × 1 optical switch and the 1 × j optical switch of the fourth embodiment do not need to be continuous integers.

(Sixth embodiment)
The sixth embodiment of the present invention is a variable dispersion compensator in which a dispersion compensation fiber is connected to the optical circuit of FIG. 2 instead of each amplification block. The signal light is first partially compensated for chromatic dispersion by the dispersion compensating fiber, and then directed to one of N paths by the 1 × N optical switch 1. After the chromatic dispersion of the signal light is compensated by the previous dispersion compensation fiber to which the signal light is directed, the chromatic dispersion compensation is repeated by the optical switch 3 by the next dispersion compensation fiber. The signal light passes through an N × 1 optical switch after being passed through a dispersion compensating fiber length having a desired amount of chromatic dispersion, and is output. At this time, variable dispersion compensation can be obtained by changing the total length of the dispersion compensating fiber by switching the optical switch in accordance with the use conditions such as the input signal light power and the environmental temperature.

  In the optical circuit of FIG. 2, the dispersion compensation amount changes discretely in dispersion compensation units depending on the fiber length of each dispersion compensation fiber. Therefore, by connecting a continuously variable dispersion compensator to the dispersion compensator of this embodiment, a dispersion compensation amount range that cannot be realized by a single continuously variable dispersion compensator can be realized.

(Seventh embodiment)
The seventh embodiment of the present invention is a variable optical delay device in which an optical delay waveguide is connected to the optical circuit of FIG. 2 instead of each amplification block. The signal light is first given an optical delay by the optical delay waveguide and then directed to any one of N paths by the 1 × N optical switch 1. The optical delay is repeated in the next optical delay waveguide by the optical switch 3 after the optical delay is given to the optical delay waveguide to which the signal light is directed. The signal light passes through an optical delay waveguide length that is a desired optical delay amount, and then passes through an N × 1 optical switch and is output. At this time, a variable spectral delay can be obtained by changing the total length of the optical delay waveguide by switching the optical switch according to the use conditions, for example, the input signal light power and the environmental temperature.

  In the optical circuit of FIG. 2, the optical delay amount changes discretely in units of optical delay amount depending on the length of each optical delay waveguide. For this reason, by connecting a continuously variable optical delay device to the optical delay device of the present embodiment, an optical delay amount range that cannot be realized by a single continuously variable optical delay device can be realized.

  As described above, in the optical amplifier using the optical circuit of the present invention, the combination of the amplification optical fibers can be changed by switching the optical switch, and as a result, the total of the amplification optical fibers through which the signal light passes. A variable gain can be obtained by changing the length of. The optical circuit of the present invention switches the combination of amplification optical fibers in response to changes in the input signal light power, and always performs optical amplification with an amplification optical fiber of an appropriate length, so that it has a wide input signal light power dynamic range. The pump light power is not wasted, and it has the advantages of high efficiency and low noise. This advantage also has the advantage that it is not necessary to use a plurality of optical amplifiers separately in system operation.

  The variable dispersion compensator using the optical circuit of the present invention and the variable optical delay device also have the same advantages as the optical amplifier of the present invention.

1, 101, 201, 901 1 × N optical switch 2, 102, 202, 902 N × 1 optical switch 5 Variable optical attenuator 6, 340 Dynamic gain equalizer 11 Amplifying optical fiber 12 Multiplexer / demultiplexer 13 Light Isolator 20, 120, 310 V-groove glass block 21, 121 Fiber 300 Planar lightwave circuit 301 1 × 3 optical switch 302 3 × 1 optical switch

Claims (10)

An optical circuit,
The optical circuit includes one main input port, N sub input ports, one 1 × N main optical switch, one N × 1 main optical switch, and 1 × j sub optical switch. N−1 1 × j subordinate optical switches where j is an integer of 2 to N and i × 1 subordinate switches, where N is an integer of 2 to N. I × 1 slave optical switch, N slave output ports, and one master output port,
The main input port is connected to an input port of the 1 × N main optical switch, and each of N−1 sub input ports among the N sub input ports is N−1 ones. × j Connected to each input port of the slave optical switch and connected to one of the N slave input ports not connected to the input port of the N−1 1 × j slave optical switch. The input port is connected to one of the N input ports of the N × 1 main optical switch,
The main output port is connected to the output port of the N × 1 main optical switch, and each of the N−1 sub output ports among the N sub output ports is the N−1 i ports. × 1 connected to each output port of the slave optical switch, and one slave of the N slave output ports not connected to the output port of the N−1 i × 1 slave optical switch. The output port is connected to one of the N output ports of the 1 × N main optical switch,
One of the output ports of each 1 × j slave optical switch of the N−1 1 × j slave optical switches is the one of the N input ports of the N × 1 master optical switch. Connected to each of the N−1 input terminals of the N × 1 main optical switch not connected to the slave input port;
Of the N output ports of the 1 × N master optical switch, N−1 output ports of the 1 × N master optical switch that are not connected to the one slave output port are N−1. Connected to each input port of the i × 1 slave switch
Of the output ports of the kth 1 × j slave optical switch of the N−1 1 × j slave optical switch, j−1 output ports not connected to the input port of the N × 1 master optical switch Are each of i−1 non-connected to the output ports of the 1 × N master optical switch among the input ports of the l-th i × 1 slave optical switch of the N−1 i × 1 slave optical switch. Are connected so as to satisfy the condition that l is an integer greater than or equal to k.
By switching the 1 × N master optical switch and / or the N−1 1 × j slave optical switches, the one master input port, the N slave input ports, and the N slave outputs. A combination of connections between a port and the one main output port can be switched.   2. The optical circuit according to claim 1, further comprising a variable optical attenuator before or after the N−1 i × 1 slave optical switches or after the N−1 1 × j slave optical switches. .   Dynamic gain equalization means for making the difference between the peak and dip of the loss spectrum variable before or after the N−1 i × 1 subordinate optical switches or after the N−1 1 × j subordinate optical switches. The optical circuit according to claim 1, further comprising: The 1 × N master optical switch, the N × 1 master optical switch, the N−1 i × 1 slave optical switches, the N−1 1 × j slave optical switches, and the variable optical attenuation. The light according to any one of claims 1 to 3, wherein at least two or more of the amplifier and the dynamic gain equalization means are integrated in a single waveguide substrate. circuit. An optical amplifier,
The optical amplifier includes one main input port, N sub input ports, one 1 × N main optical switch, one N × 1 main optical switch, and 1 × j sub optical switch. N−1 1 × j subordinate optical switches where j is an integer of 2 to N and i × 1 subordinate switches, where N is an integer of 2 to N. I × 1 slave optical switch, N slave output ports, one master output port, and N optical amplifying optical fibers,
The main input port is connected to an input port of the 1 × N main optical switch, and each of N−1 sub input ports among the N sub input ports is N−1 ones. × j Connected to each input port of the slave optical switch and connected to one of the N slave input ports not connected to the input port of the N−1 1 × j slave optical switch. The input port is connected to one of the N input ports of the N × 1 main optical switch,
The main output port is connected to the output port of the N × 1 main optical switch, and each of the N−1 sub output ports among the N sub output ports is the N−1 i ports. × 1 connected to each output port of the slave optical switch, and one slave of the N slave output ports not connected to the output port of the N−1 i × 1 slave optical switch. The output port is connected to one of the N output ports of the 1 × N main optical switch,
One of the output ports of each 1 × j slave optical switch of the N−1 1 × j slave optical switches is the one of the N input ports of the N × 1 master optical switch. Connected to each of the N−1 input terminals of the N × 1 main optical switch not connected to the slave input port;
Of the N output ports of the 1 × N master optical switch, N−1 output ports of the 1 × N master optical switch that are not connected to the one slave output port are N−1. Connected to each input port of the i × 1 slave switch
Of the output ports of the kth 1 × j slave optical switch of the N−1 1 × j slave optical switch, j−1 output ports not connected to the input port of the N × 1 master optical switch Are each of i−1 non-connected to the output ports of the 1 × N master optical switch among the input ports of the l-th i × 1 slave optical switch of the N−1 i × 1 slave optical switch. Are connected so as to satisfy the condition that l is an integer greater than or equal to k.
By switching the 1 × N master optical switch and / or the N−1 1 × j slave optical switches, the one master input port, the N slave input ports, and the N slave outputs. A combination of connections between the port and the one main output port can be switched;
The N slave output ports are connected to input ports of the N optical amplification optical fibers, respectively.
The output port of the optical amplification optical fiber connected to the one slave output port among the N optical amplification optical fibers is j = N of the N−1 1 × j slave optical switches. Connected to a slave input port connected to a 1 × j slave optical switch
Of the N optical amplification optical fibers, light connected to a slave output port connected to an i × 1 slave switch satisfying i = N among the N−1 i × 1 slave switches. The output port of the amplification optical fiber is connected to the one slave input port,
Of the N optical amplification optical fibers, optical amplification connected to the N-1 slave output ports connected to the output ports of the N-1 i × 1 slave switch. The output ports of the optical fiber are connected to the N-1 sub input ports connected to the output ports of the N-1 1 × j sub optical switches so that j = N−i + 1 is satisfied. And
By switching the 1 × N main optical switch and / or the N−1 1 × j sub-optical switches, the length of the optical amplifying optical fiber is changed by switching the combination of the optical amplifying optical fibers. An optical amplifier characterized in that the amplification factor can be changed.   6. The optical amplifier according to claim 5, further comprising a variable optical attenuator before or after the N−1 i × 1 slave optical switches or after the N−1 1 × j slave optical switches. .   Dynamic gain equalization means for making the difference between the peak and dip of the loss spectrum variable before or after the N−1 i × 1 subordinate optical switches or after the N−1 1 × j subordinate optical switches. The optical amplifier according to claim 5 or 6, further comprising: The 1 × N master optical switch, the N × 1 master optical switch, the N−1 i × 1 slave optical switches, the N−1 1 × j slave optical switches, and the variable optical attenuation. vessels and, more at least two of said dynamic gain equalization means, the light according to any one of claims 5 to 7, characterized in that it is integrated into a single waveguide substrate amplifier. A tunable dispersion compensator,
The tunable dispersion compensator includes one main input port, N sub input ports, one 1 × N main optical switch, one N × 1 main optical switch, and 1 × j sub light. N−1 1 × j slave optical switches in which j is an integer of 2 to N, and i × 1 slave switches, where i is an integer of 2 to N. 1 i × 1 slave optical switch, N slave output ports, 1 master output port, and N dispersion compensating fibers,
The main input port is connected to an input port of the 1 × N main optical switch, and each of N−1 sub input ports among the N sub input ports is N−1 ones. × j Connected to each input port of the slave optical switch and connected to one of the N slave input ports not connected to the input port of the N−1 1 × j slave optical switch. The input port is connected to one of the N input ports of the N × 1 main optical switch,
The main output port is connected to the output port of the N × 1 main optical switch, and each of the N−1 sub output ports among the N sub output ports is the N−1 i ports. × 1 connected to each output port of the slave optical switch, and one slave of the N slave output ports not connected to the output port of the N−1 i × 1 slave optical switch. The output port is connected to one of the N output ports of the 1 × N main optical switch,
One of the output ports of each 1 × j slave optical switch of the N−1 1 × j slave optical switches is the one of the N input ports of the N × 1 master optical switch. Connected to each of the N−1 input terminals of the N × 1 main optical switch not connected to the slave input port;
Of the N output ports of the 1 × N master optical switch, N−1 output ports of the 1 × N master optical switch that are not connected to the one slave output port are N−1. Connected to each input port of the i × 1 slave switch
Of the output ports of the kth 1 × j slave optical switch of the N−1 1 × j slave optical switch, j−1 output ports not connected to the input port of the N × 1 master optical switch Are each of i−1 non-connected to the output ports of the 1 × N master optical switch among the input ports of the l-th i × 1 slave optical switch of the N−1 i × 1 slave optical switch. Are connected so as to satisfy the condition that l is an integer greater than or equal to k.
By switching the 1 × N master optical switch and / or the N−1 1 × j slave optical switches, the one master input port, the N slave input ports, and the N slave outputs. A combination of connections between the port and the one main output port can be switched;
The N slave output ports are respectively connected to input ports of the N dispersion compensating fibers,
The output port of the dispersion compensating fiber connected to the one slave output port among the N dispersion compensating fibers is 1 × satisfying j = N among the N−1 1 × j slave optical switches. j It is connected to the slave input port connected to the slave optical switch,
Dispersion compensating fiber connected to a slave output port connected to an i × 1 slave optical switch satisfying i = N among the N−1 i × 1 slave optical switches of the N dispersion compensating fibers. Are connected to the one slave input port,
Of the N dispersion compensating fibers, the output of the dispersion compensating fiber connected to the N−1 slave output ports connected to the output ports of the N−1 i × 1 slave optical switches. The ports are connected to the N-1 slave input ports connected to the output ports of the N-1 1 * j slave optical switches so as to satisfy j = N-i + 1.
By switching the 1 × N master optical switch and / or the N−1 1 × j slave optical switches, the length of the dispersion compensating fiber is changed by changing the combination of the dispersion compensating fibers, and thus the dispersion compensation amount is changed. variable dispersion compensator characterized in that it can be. A variable optical delay device,
The variable optical delay unit includes one master input port, N slave input ports, one 1 × N master optical switch, one N × 1 master optical switch, and 1 × j slave light. N−1 1 × j slave optical switches in which j is an integer of 2 to N, and i × 1 slave switches, where i is an integer of 2 to N. One i × 1 slave optical switch, N slave output ports, one master output port, and N optical delay waveguides,
The main input port is connected to an input port of the 1 × N main optical switch, and each of N−1 sub input ports among the N sub input ports is N−1 ones. × j Connected to each input port of the slave optical switch and connected to one of the N slave input ports not connected to the input port of the N−1 1 × j slave optical switch. The input port is connected to one of the N input ports of the N × 1 main optical switch,
The main output port is connected to the output port of the N × 1 main optical switch, and each of the N−1 sub output ports among the N sub output ports is the N−1 i ports. × 1 connected to each output port of the slave optical switch, and one slave of the N slave output ports not connected to the output port of the N−1 i × 1 slave optical switch. The output port is connected to one of the N output ports of the 1 × N main optical switch,
One of the output ports of each 1 × j slave optical switch of the N−1 1 × j slave optical switches is the one of the N input ports of the N × 1 master optical switch. Connected to each of the N−1 input terminals of the N × 1 main optical switch not connected to the slave input port;
Of the N output ports of the 1 × N master optical switch, N−1 output ports of the 1 × N master optical switch that are not connected to the one slave output port are N−1. Connected to each input port of the i × 1 slave switch
Of the output ports of the kth 1 × j slave optical switch of the N−1 1 × j slave optical switch, j−1 output ports not connected to the input port of the N × 1 master optical switch Are each of i−1 non-connected to the output ports of the 1 × N master optical switch among the input ports of the l-th i × 1 slave optical switch of the N−1 i × 1 slave optical switch. Are connected so as to satisfy the condition that l is an integer greater than or equal to k.
By switching the 1 × N master optical switch and / or the N−1 1 × j slave optical switches, the one master input port, the N slave input ports, and the N slave outputs. A combination of connections between the port and the one main output port can be switched;
The N slave output ports are respectively connected to input ports of the N optical delay waveguides,
The output port of the optical delay waveguide connected to the one slave output port among the N optical delay waveguides satisfies j = N among the N-1 1 × j slave optical switches. Connected to a slave input port connected to a 1 × j slave optical switch,
Of the N optical delay waveguides, the optical delay connected to the slave output port connected to the i × 1 slave optical switch satisfying i = N among the N−1 i × 1 slave optical switches. The output port of the waveguide is connected to the one slave input port,
Of the N optical delay waveguides, the optical delay waveguides connected to the N-1 slave output ports connected to the output ports of the N-1 i × 1 slave optical switches, respectively. Are connected to the N−1 slave input ports connected to the output ports of the N−1 1 × j slave optical switches so that j = N−i + 1 is satisfied. ,
By switching the 1 × N master optical switch and / or the N−1 1 × j slave optical switches, the length of the optical delay waveguide is changed by switching the combination of the optical delay waveguides, and thus the amount of optical delay A variable optical delay device, characterized in that can be changed.

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