JP4443559B2 - Optical phase modulation evaluation device - Google Patents

Description

  The present invention relates to an optical phase modulation evaluation apparatus that evaluates an optical phase modulation signal in which an optical carrier wave in a coherent optical communication system is phase modulated (for example, DPSK, DQPSK, etc.) by a data signal. It is related with the optical phase modulation evaluation apparatus which can perform evaluation of correctly.

  Conventionally, as an optical phase modulation evaluation apparatus for evaluating an optical phase modulation signal in which an optical carrier wave is phase-modulated by a data signal at a predetermined symbol rate, optical phase detection of the optical phase modulation signal is performed by a bit delay interferometer. Some have evaluated the phase modulation characteristics of the phase modulation signal (see, for example, Patent Document 1).

  FIG. 12 shows a schematic configuration of this type of optical phase modulation evaluation apparatus. An optical phase modulation signal, which is light to be measured by the optical phase modulation evaluation apparatus, is generated by phase-modulating an optical carrier wave with a data signal at a predetermined symbol rate, and a bit delay interferometer 20 as an optical phase detector. Is input. The bit delay interferometer 20 is composed of a Mach-Zehnder interferometer using an optical waveguide. The optical phase modulation signal input from the port 20a and the light passing through the arm 20c by the branching unit 20b and the arm 20d (bit delay). The light passing through the arm 20c and the light passing through the arm 20d are multiplexed and interfered by the multiplexing unit 20e. Thereby, the phase change of the optical phase modulation signal is converted into a change in light intensity, and two light intensity conversion signals whose phases are different from each other by 180 ° (π) are output from the two ports 20g and 20h, respectively. The bit delay unit 20f has an optical path length of the arm 20d corresponding to the delay amount so that the delay amount (delay time difference) between the two arms becomes a delay amount (time) corresponding to one bit of the symbol rate. Is longer than the optical path length of the arm 20c.

The light receiver (PD) 21 photoelectrically converts the light intensity conversion signal output from the port 20g of the bit delay interferometer 20 and outputs an electrical signal. The signal processing unit 22 demodulates the data signal from the electrical signal output from the light receiver 21, and performs error rate measurement and waveform observation using the demodulated waveform obtained thereby to evaluate the optical phase modulation signal. .
JP-A-6-21891

  Recently, phase modulation schemes such as DPSK and DQPSK, which have high frequency efficiency, are attracting attention because of problems of fiber nonlinearity and dispersion accompanying an increase in communication traffic capacity. Depending on the method, different symbol rates are used. For example, in 40 Gbps-DPSK, the symbol rate is 40 Gbps, and in 40 Gbps-DQPSK, the symbol rate is 20 Gbps. As described above, in a situation where different symbol rates are used depending on the system, a single optical phase modulation evaluation apparatus can support a plurality of symbol rates as an optical phase modulation evaluation apparatus for evaluating an optical phase modulation signal. It is desired.

  However, in the above conventional optical phase modulation evaluation apparatus, since the delay amount corresponding to one bit of the symbol rate set by the bit delay unit 20f is fixed with respect to the specific symbol rate, the optical phase When the symbol rate of the modulation signal is different from 20 Gbps or 40 Gbps as described above, there is a problem that only the optical phase modulation signal of one of the symbol rates can be evaluated.

  The present invention enables a bit delay unit of a bit delay interferometer to set a delay amount corresponding to each of a plurality of symbol rates of an optical phase modulation signal and corresponding to one bit of those symbol rates, An object of the present invention is to solve these problems and provide an optical phase modulation evaluation apparatus capable of accurately evaluating optical phase modulation signals having different symbol rates.

In order to solve the above-described problem, in the optical phase modulation evaluation apparatus according to claim 1 of the present invention, the optical carrier receives the optical phase modulation signal (b) obtained by phase-modulating the data carrier signal with a predetermined symbol rate. The first light passing through the first optical path including the one corner mirror (2a) and the second light passing through the second optical path including the second corner mirror (3). The first light that has been reflected and returned by the first corner mirror and the second light that has been reflected and returned by the second corner mirror are combined to interfere with each other. A beam splitter (1) for outputting a light intensity conversion signal (c1, c2) obtained by converting a phase modulation signal, and a bit delay (2) for setting a delay amount corresponding to 1 bit of the symbol rate. Having a Michelson-type bit slow An interferometer (10), and an optical waveform measuring unit (11) for converting the optical intensity conversion signals (c1, c2) output from the bit delay interferometer into electrical signals and observing the waveform of the optical phase modulation signal; A delay amount for receiving a symbol rate designation signal for designating the symbol rate of the optical phase modulation signal and setting a delay amount of the bit delay unit based on the symbol rate designation signal Setting means (12) was provided.

  Also, in the optical phase modulation evaluation apparatus according to claim 2 of the present invention, in the optical phase modulation evaluation apparatus according to claim 1 described above, the bit delay unit is configured by the first corner mirror, The corner mirror is moved in a direction parallel to the first optical path so that the delay amount corresponding to each of the plurality of symbol rates can be set.

  Also, in the optical phase modulation evaluation apparatus according to claim 3 of the present invention, in the optical phase modulation evaluation apparatus according to claim 1 described above, the bit delay unit provides a delay amount corresponding to one bit of the plurality of symbol rates. A plurality of parallel plates (2b, 2c) of a transparent material having a thickness for switching to the first optical path corresponding to the plurality of symbol rates. The delay amount corresponding to can be set.

  In the optical phase modulation evaluation apparatus according to claim 4 of the present invention, in the optical phase modulation evaluation apparatus according to claim 1 described above, the bit delay unit includes a symbol rate obtained by removing a specific symbol rate from the plurality of symbol rates. And a parallel plate (2e) of a transparent material having a thickness for providing a predetermined delay amount corresponding to the first corner mirror, and the first corner mirror has a delay amount corresponding to the specific symbol rate. As described above, the position in the direction parallel to the first optical path is fixed, and the parallel plate sets a delay amount corresponding to 1 bit in the first optical path at a symbol rate other than the specific symbol rate. I was able to do it.

In the optical phase modulation evaluation apparatus according to claim 5 of the present invention, in the optical phase modulation evaluation apparatus according to claim 1, the bit delay unit has a predetermined delay amount corresponding to each of the plurality of symbol rates. A plurality of pairs of _two parallel plates (2f ₁ , 2f ₂ , 2g ₁ , 2g ₂ ) of a transparent material having a thickness to give, and each of the symbol rates is 1 It is arranged in a square shape so as to give a delay amount corresponding to a bit, and a delay amount corresponding to one bit can be set by switching to the first optical path corresponding to a plurality of the symbol rates. did.

The optical phase modulation evaluation apparatus according to claim 6 of the present invention is the optical phase modulation evaluation apparatus according to claim 1, wherein the bit delay unit is a symbol rate obtained by removing a specific symbol rate from the plurality of symbol rates. And a pair of _two parallel plates (2h ₁ , 2h ₂ ) made of a transparent material having a thickness for giving a predetermined delay amount corresponding to the first corner mirror. The position in the direction parallel to the first optical path is fixed so as to obtain a delay amount corresponding to the symbol rate, and further, the pair of parallel plates provides a predetermined delay amount corresponding to the symbol rate. The first optical path can be set at a symbol rate other than the specific symbol rate.

  In the optical phase modulation evaluation apparatus according to claim 7 of the present invention, any one of the first and second optical paths of the bit delay interferometer in the optical phase modulation evaluation apparatus according to any one of claims 1 to 6 described above. An optical phase delay device (4) that is provided on either side and can arbitrarily set a delay amount that can be changed by one period of the optical phase difference between the two optical paths, and sets the delay amount of the optical phase delay device Phase control means (13).

  Further, in the optical phase modulation evaluation apparatus according to claim 8 of the present invention, in the optical phase modulation evaluation apparatus according to claim 7, the optical phase delay device is configured by the second corner mirror, An arbitrary delay amount can be set by moving the two corner mirrors in a direction parallel to the second optical path.

  The optical phase modulation evaluation apparatus according to claim 9 of the present invention is the optical phase modulation evaluation apparatus according to claim 7 described above, wherein the optical phase delay has a thickness having a thickness for giving a predetermined delay amount. A parallel plate (4a) made of a material, which can be set to an arbitrary delay amount by rotating the parallel plate and changing the incident angle of light to the parallel plate.

The optical phase modulation evaluation apparatus according to claim 10 of the present invention is the optical phase modulation evaluation apparatus according to claim 7 described above, wherein the optical phase delay has a thickness having a thickness for giving a predetermined delay amount. A pair of _two parallel plates (4b ₁ , 4b ₂ ) made of material, the pair of parallel plates being arranged in a square shape so that the incident angle and the outgoing angle of light are substantially equal. An arbitrary delay amount can be set by rotating at least one of the parallel plates to change the incident angle of the light to the parallel plate.

  Further, in the optical phase modulation evaluation apparatus according to claim 11 of the present invention, in the optical phase modulation evaluation apparatus according to any one of claims 1 to 10 described above, the bit delay interferometer includes two signals output from the beam splitter. In order to give a relative delay time to the light intensity conversion signal, an optical output signal delay device (5) for changing the optical path length of one of the two optical paths through which the light intensity conversion signal passes is provided.

  In the optical phase modulation evaluation apparatus according to the first to sixth aspects of the present invention, the bit delay unit of the bit delay interferometer corresponds to each of a plurality of symbol rates of the optical phase modulation signal and corresponds to one bit of those symbol rates. Since the delay amount to be set can be set, the waveforms of the optical phase modulation signals having different symbol rates can be accurately observed. Accordingly, it is possible to accurately evaluate the phase modulation state of the optical phase modulation signal in DPSK, DQPSK, or multilevel modulation with different symbol rates with one optical phase modulation evaluation apparatus.

  In the optical phase modulation evaluation apparatus according to claims 7 to 10 of the present invention, one of the first and second optical paths of the bit delay interferometer can be changed by one period of the optical phase difference between the two optical paths. Since an optical phase retarder that can arbitrarily set a delay amount is provided, the optical phase difference between the two optical paths can be adjusted to π / 2 radians or 0 even when environmental conditions such as temperature change. Thereby, it is possible to set an arbitrary relative phase difference between bits.

  In the optical phase modulation evaluation apparatus according to claim 11 of the present invention, the bit delay interferometer gives the relative delay time to the two light intensity conversion signals output from the beam splitter, so that the two light intensities are given. Since an optical output signal delay device for changing the delay time of the optical path is provided in either one of the optical paths through which the converted signal passes, for example, when receiving two optical output signals of the bit delay interferometer in a balanced manner, 2 The phase difference between the modulation signals of the two light intensity conversion signals can be accurately matched.

  Embodiments of the present invention will be described below.

[First Embodiment]
The configuration of the optical phase modulation evaluation apparatus according to the first embodiment of the present invention is shown in FIG. An optical phase modulation signal, which is light to be measured by the optical phase modulation evaluation apparatus, is generated by phase-modulating an optical carrier wave with a data signal at a predetermined symbol rate, and is input to the bit delay interferometer 10. The bit delay interferometer 10 is composed of a Michelson interferometer using a spatial propagation path, and an input optical phase modulation signal is converted by a beam splitter (BS) 1 into a corner mirror 2a as a bit delay device 2. Are split into first light passing through the first optical path configured to include the second light passing through the second optical path configured including the corner mirror 3, and reflected by the corner mirror 2a. The returned first light and the second light reflected and returned by the corner mirror 3 are combined and interfered. Thereby, the phase change of the optical phase modulation signal is converted into a change in light intensity, and two light intensity conversion signals whose phases are different from each other by 180 ° (π) are output from the beam splitter 1.

  The bit delay unit 2 is configured by the corner mirror 2a, and a delay amount (delay time difference) between the two first and second optical paths is equivalent to one bit of the symbol rate (delay amount). The optical path length of the first optical path is made longer than the optical path length of the second optical path by the amount of delay so that the corner mirror 2a is parallel to the first optical path so as to correspond to the symbol rate. You can move in the direction you want. The corner mirror 2a is moved based on a command from the delay amount setting means 12.

The amount of movement L of the corner mirror 2a with respect to the symbol rate (the amount of movement from a state where there is no optical path length difference between the two optical paths) is obtained as follows. That is, when the symbol rate is SR [bps], the delay time t [sec] corresponding to 1 bit is t = 1 / SR. The movement amount L is L = (c × t) / 2. Here, c is the speed of light. As a specific example, when SR = 40 Gbps, t = 25 ps and L ₁ = 3.25 mm. When SR = 20 Gbps, t = 50 ps and L ₂ = 7.5 mm.

  The above-described corner mirror 2 a constitutes the bit delay device 2 as described above, and reflects the first light input from the beam splitter 1 and returns it to the beam splitter 1. The corner mirror 3 described above reflects the second light input from the beam splitter 1 and returns it to the beam splitter 1.

  Next, the optical waveform measurement unit 11 converts one of two light intensity conversion signals output from the bit delay interferometer 10 and having a phase difference of 180 ° (π) into an electrical signal (O / E conversion). Then, data processing of the obtained electric signal waveform is performed to observe the waveform of the optical phase modulation signal, measure the phase modulation characteristic, and the like. An optical sampling oscilloscope can be used as the optical waveform measurement unit 11. FIG. 1 shows the case where one of the two light intensity conversion signals is input to the optical waveform measuring unit 11, that is, the case of single reception, but both the two light intensity conversion signals are input. Also good. In that case, the optical waveform measuring unit 11 can perform balanced reception, and the light receiving sensitivity of the measurement can be improved as compared with the case of single reception.

The delay amount setting means 12 receives a symbol rate designation signal (designates the symbol rate of the optical phase modulation signal) input from an operation unit or the like (not shown), and based on this symbol rate designation signal, the bit delay unit 2 Set the delay amount. Specifically, when the symbol rate designation signal designates a symbol rate of 40 Gbps, the corner mirror 2a as the bit delay unit 2 is moved by L ₁ = 3.25 mm, and a symbol rate of 20 Gbps is designated. In this case, the corner mirror 2a is controlled to move L ₂ = 7.5 mm.

  The bit delay unit 2 of the first embodiment may be one shown in FIGS. 2 to 6 in addition to that shown in FIG.

That is, in the bit delay unit 2 shown in FIG. 2, a transparent material (thickness d ₁ for providing a delay amount corresponding to one bit of one symbol rate so as to correspond to two kinds of symbol rates ( From the delay amount setting means 12, a parallel plate 2 b made of a transparent material having a thickness d ₂ for giving a delay amount corresponding to one bit of the other symbol rate is provided. Based on this command, it is moved and switched in a direction orthogonal to the optical path. In this case, the position of the corner mirror 2a is fixed so that the optical path lengths of the two optical paths are equal in a state where neither of the two parallel plates 2b and 2c is set as the optical path.

The thickness d of the parallel plate with respect to the symbol rate is determined by using the delay time t = 1 / SR [sec] (SR: symbol rate [bps]) corresponding to 1 bit described above, and d = (c × t) / 2. It is calculated | required by (n-1). Here, n is the refractive index of the parallel plate (transparent material), and c is the speed of light. A specific example when glass (n = 1.5) is used for the parallel plate will be t = 25 ps and d = 7.5 mm when SR = 40 Gbps. When SR = 20 Gbps, t = 50 ps and d = 15 mm. Therefore, when the symbol rate is 40 Gbps, the glass parallel plate 2b with d ₁ = 7.5 mm may be inserted into the optical path, and when the symbol rate is 20 Gbps, the glass parallel plate 2c with d ₂ = 15 mm may be inserted into the optical path. . Here, a case where two types of symbol rates are supported has been described, but the same applies even if the number of symbol rates increases. In FIG. 2, the first light is transmitted through the parallel plates 2b and 2c twice. However, the parallel plates 2b and 2c may be inserted into the optical path so as to be transmitted only once. In that case, the thickness of each of the parallel plates 2b and 2c is twice the above (d ₁ = 15 mm, d ₂ = 30 mm).

Further, the bit delay device 2 shown in FIG. 3, have on two symbol rate, and corner mirrors 2a, is inserted into the first optical path, the thickness d ₃ for providing a predetermined delay amount A delay amount corresponding to one bit of each symbol rate is set with a parallel plate 2e made of a transparent material (for example, glass, silicon, etc.). That is, the position of the corner mirror 2a is fixed so as to correspond to one symbol rate, and the parallel plate 2e is adapted to the optical path based on the command from the delay amount setting means 12 so as to correspond to the other symbol rate. Inserted in a direction perpendicular to the direction.

Fixing the position of the corner mirror 2a for the case of SR = 40 Gbps and SR = 20 Gbps, the thickness _{d 3} of the parallel plate 2e is as follows. That is, the fixed position of the corner mirror 2a is L ₁ = 3.25 mm corresponding to SR = 40 Gbps and the above-described movement amount L (movement amount from a state where there is no optical path length difference between the two optical paths). Then, the thickness d ₃ of the parallel plate 2e is set to correspond to SR = 20 Gbps, and the difference (ΔL = L ₂ −L ₁ = 3. 25 mm), the optical path length is determined to be increased. Therefore, the thickness _{d 3} of the parallel plate 2e is obtained in d described above = (c × t) / 2 (n-1). Here, since (c × t) / 2 is the difference ΔL = 3.25 mm, when glass (n = 1.5) is used for the parallel plate 2e, d ₃ = 7.5 mm. Here, a case where two types of symbol rates are supported has been described, but the same applies even if the number of symbol rates increases. In FIG. 3, the first light is transmitted through the parallel plate 2e twice. However, the parallel plate 2e may be inserted into the optical path so as to transmit only once. In this case, the thickness of the parallel plate 2e is twice the above (d ₃ = 15 mm).

Further, in the bit delay device 2 shown in FIG. 4, a transparent material (for example, glass) having a thickness d ₄ for giving a predetermined delay amount corresponding to the symbol rate so as to correspond to two kinds of symbol rates. Two parallel plates 2f ₁ , 2f ₂ made of silicon, etc.) and two parallel plates 2g ₁ , 2g ₂ made of a transparent material having a thickness d ₅ in pairs. The parallel plates 2f ₁ , 2f ₂ and the parallel plates 2g ₁ , 2g ₂ of the pair of C are shaped like a letter C so that the incident angle and the outgoing angle of the light are equal to each other and a delay amount corresponding to one bit of the symbol rate is given. Placed in the mold. The two pairs corresponding to the two types of symbol rates are moved and switched in a direction orthogonal to the optical path based on a command from the delay amount setting means 12. In this case, the position of the corner mirror 2a is fixed so that the optical path lengths of the two optical paths are equal in a state where none of the two pairs is set as the optical path.

As described above, the two parallel plates 2f ₁ , 2f ₂ and the parallel plates 2g ₁ , 2g ₂ are arranged in a C shape in each pair, so that the reflection from the bit delay unit 2 to the beam splitter 1 is performed. And the movement of the light beam (beam shift) at the time of switching the delay amount can be suppressed. When the beam shift is large, the interference intensity is affected. Here, a case where two types of symbol rates are supported has been described, but the same applies even if the number of symbol rates increases. When the two pairs are inserted into the first optical path, the parallel plates 2f ₁ and 2f ₂ and the parallel plates 2g ₁ and 2g ₂ may be arranged in a square shape as shown in FIG. .

Further, the bit delay device 2 shown in FIG. 6 has for two types of the symbol rate, and corner mirrors 2a, is inserted into the first optical path, the thickness d ₆ for giving a predetermined delay amount Two parallel plates 2h ₁ , 2h ₂ made of a transparent material (for example, glass, silicon, etc.) (the two parallel plates 2h ₁ , 2h ₂ have a symbol rate such that the incident angle and the outgoing angle of light are equal) A delay amount corresponding to one bit of each symbol rate is set with a pair of (corresponding to a C-shaped shape so as to give a corresponding predetermined delay amount). That is, the position of the corner mirror 2a is fixed so as to correspond to one symbol rate, and the pair is placed on the optical path based on a command from the delay amount setting means 12 so as to correspond to the other symbol rate. It is moved and inserted in a direction perpendicular to the direction.

The fixed position of the corner mirror 2a in the case of SR = 40 Gbps and SR = 20 Gbps, the thickness d _{6 of the two} parallel plates 2h ₁ and 2h ₂ are as follows. That is, the fixed position of the corner mirror 2a is L ₁ = 3.25 mm corresponding to SR = 40 Gbps and the above-described movement amount L (movement amount from a state where there is no optical path length difference between the two optical paths). The thickness d _{6 of the two} parallel plates 2h ₁ and 2h ₂ corresponds to SR = 20 Gbps, and the difference (ΔL = L) of the movement amount L of the corner mirror 2a of SR = 20 Gbps with respect to SR = 40 Gbps described above. ₂₋ L ₁ = 3.25 mm) so that the optical path length is increased.

As described above, by arranging the _two parallel plates 2h ₁ and 2h ₂ in a C shape, reflection from the bit delay unit 2 to the beam splitter 1 can be prevented, and the beam at the time of switching the delay amount can be prevented. Shift can be suppressed. Here, a case where two types of symbol rates are supported has been described, but the same applies even if the number of symbol rates increases. In FIG. 6, the first light is transmitted through the pair twice. However, the pair may be inserted into the optical path so that the first light is transmitted only once.

[Second Embodiment]
FIG. 7 shows the configuration of an optical phase modulation evaluation apparatus according to the second embodiment of the present invention. The first embodiment shown in FIG. 1 is such that the second optical path of the bit delay interferometer 10 described above is changed by one cycle of the optical phase difference between the first optical path and the second optical path. Is provided with an optical phase delay 4 that can be arbitrarily set, and the optical phase delay 4 is constituted by the corner mirror 3, and the corner mirror 3 is parallel to the second optical path based on the control from the phase control means 13. The only difference is that the delay amount of the optical phase retarder 4 can be set arbitrarily by moving in the direction. Therefore, the description is omitted.

  The optical phase retarder 4 of the second embodiment may be the one shown in FIGS. 8 and 9 in addition to the one shown in FIG.

That is, in the optical phase delay device 4 shown in FIG. 8, the optical phase delay device 4 is arranged in the first optical path as shown in FIG. 8, and has a thickness d ₇ for giving a predetermined delay amount. It is comprised with the parallel plate 4a of material (for example, glass, silicon, etc.). Based on a command from the phase control means 13, the parallel plate 4a is rotated to change the incident angle of light to the parallel plate 4a, so that an arbitrary delay amount can be set. In the case of this configuration, the beam shift is generated by the rotation of the parallel plate 4a, but the amount thereof is small on the order of wavelength and hardly affects the interference intensity. In FIG. 8, the optical phase retarder 4 is provided in the first optical path, but may be provided in the second optical path. In FIG. 8, the first light is transmitted twice through the parallel plate 4a. However, the parallel plate 4a may be inserted into the optical path so that it is transmitted only once.

Further, in the optical phase retarder 4 shown in FIG. 9, two parallel plates 4b ₁ and 4b ₂ made of a transparent material (for example, glass, silicon, etc.) having a thickness d ₈ for giving a predetermined delay amount are provided. As a pair, the parallel plates 4b ₁ and 4b ₂ of the pair are arranged in a square shape so that the incident angle and the outgoing angle of light are substantially equal. Then, based on a command from the phase control means 13, two rotating at least one of parallel plate 4b _1, 4b ₂ by changing the incident angle of light to this parallel plate 4b _1, 4b ₂ An arbitrary delay amount can be set. The parallel plates 4b ₁ and 4b ₂ in a pair are arranged in a square shape so that the incident angle and the outgoing angle of light are equal, and the parallel plates 4b ₁ and 4b ₂ are interlocked to be opposite to each other. In the case of rotation, it is possible to suppress reflection and to suppress a beam shift when setting a delay amount. In FIG. 9, the optical phase delay 4 is provided in the first optical path, but may be provided in the second optical path.

[Third Embodiment]
The configuration of the optical phase modulation evaluation apparatus according to the third embodiment of the present invention is shown in FIG. The second embodiment shown in FIG. 7 is different from the above two light intensity conversions in one of the optical paths through which the two light intensity conversion signals output from the beam splitter 1 of the bit delay interferometer 10 described above pass. The only difference is that an optical output signal delay device 5 for changing the optical path length of the one optical path for providing a relative delay time to the signal is provided.

  As shown in FIG. 10, the optical output signal delay unit 5 is composed of four mirrors 5a, 5b, 5c, and 5d and a movable part (not shown). Of these, the two mirrors 5a and 5b form a corner mirror, and are movable. The part moves the corner mirror in the direction of the arrow. Then, the corner mirror is moved to vary the optical path length between the mirror 5b and the mirror 5c and between the mirror 5a and the mirror 5d, thereby adjusting the phase difference between the two light intensity conversion signals.

The figure which shows the structure of 1st Embodiment of this invention. The figure for demonstrating another structure of the bit delay device of this invention The figure for demonstrating another structure of the bit delay device of this invention The figure for demonstrating another structure of the bit delay device of this invention The figure for demonstrating another structure of the bit delay device of this invention The figure for demonstrating another structure of the bit delay device of this invention The figure which shows the structure of 2nd Embodiment of this invention. The figure for demonstrating another structure of the optical phase delay device of this invention The figure for demonstrating another structure of the optical phase delay device of this invention The figure which shows the structure of 3rd Embodiment of this invention. The figure which shows schematic structure of a prior art example

Explanation of symbols

1 ... beam splitter (BS), 2,20f ··· bit delay unit, 2a, 3,5a, 5b ··· corner _{mirror, 2b, 2c, 2e, 2f} 1, 2f 2, 2g 1, 2g 2 , 2h ₁ , 2h ₂ , 4a, 4b ₁ , 4b ₂ ... Parallel plate, 4... Optical phase delay device, 5... Optical output signal delay device, 10, 20. DESCRIPTION OF SYMBOLS 11 ... Optical waveform measurement part, 12 ... Delay amount setting means, 13 ... Phase control means, 20a, 20g, 20h ... Port, 20b ... Demultiplexing part, 20c, 20d ... Arm, 20e ... multiplexing unit, 21 ... light receiver (PD), 22 ... signal processing unit.

Claims (11)

The optical carrier receives an optical phase modulation signal (b) obtained by phase modulation with a data signal at a predetermined symbol rate, and passes through a first optical path configured to include a first corner mirror (2a). The first light that is demultiplexed into the second light passing through the second optical path including the light and the second corner mirror (3), and returned by being reflected by the first corner mirror; A beam splitter that multiplexes and interferes with the second light reflected and returned by the second corner mirror and outputs a light intensity conversion signal (c1, c2) obtained by converting the optical phase modulation signal. Michelson type bit delay interferometer (10) having (1) and a bit delay unit (2) for setting a delay amount corresponding to one bit of the symbol rate, and output from the bit delay interferometer The light intensity conversion signal (C1, c2) in the optical phase modulation evaluating device and an optical waveform measuring unit (11) for converting into an electrical signal observing a waveform of the optical phase modulation signal,
A delay amount setting means (12) for receiving a symbol rate specifying signal for specifying the symbol rate of the optical phase modulation signal and setting a delay amount of the bit delay unit based on the symbol rate specifying signal; A characteristic optical phase modulation evaluation apparatus.   The bit delay unit (2) is composed of the first corner mirror (2a), and the first corner mirror is moved in a direction parallel to the first optical path, so that a plurality of the symbol rates are obtained. The optical phase modulation evaluation apparatus according to claim 1, wherein a delay amount corresponding to 1 bit corresponding to can be set.   The bit delay unit (2) is composed of a plurality of parallel plates (2b, 2c) made of a transparent material having a thickness for giving a delay amount corresponding to one bit of the plurality of symbol rates. 2. The optical phase modulation evaluation apparatus according to claim 1, wherein the parallel plate can switch to the first optical path corresponding to a plurality of the symbol rates and set a delay amount corresponding to one bit.   The bit delay unit (2) includes a parallel plate (2e) made of a transparent material having a thickness for providing a predetermined delay amount corresponding to a symbol rate obtained by removing a specific symbol rate from the plurality of symbol rates. The first corner mirror is fixed in a position parallel to the first optical path so as to have a delay amount corresponding to the specific symbol rate, and the parallel plate The optical phase modulation evaluation apparatus according to claim 1, wherein a delay amount corresponding to 1 bit can be set in the first optical path at a symbol rate other than a symbol rate. The bit delay unit (2) has two parallel plates (2f ₁ , 2f ₂ , 2g _{1) made of} a transparent material having a thickness for giving a predetermined delay amount corresponding to each of the plurality of symbol rates. 2g ₂ ) and a plurality of symbol rates arranged in a C shape so as to give a delay amount corresponding to one bit of each of the symbol rates. 2. The optical phase modulation evaluation apparatus according to claim 1, wherein a delay amount corresponding to one bit can be set by switching to the first optical path corresponding to the first. Two parallel plates (2h) of a transparent material having a thickness for the bit delay unit (2) to give a predetermined delay amount corresponding to a symbol rate obtained by removing a specific symbol rate from the plurality of symbol rates. ₁ and 2h ₂ ), and the first corner mirror is fixed in a position parallel to the first optical path so as to have a delay amount corresponding to the specific symbol rate, Further, the pair of parallel plates are arranged in a square shape so as to give a predetermined delay amount corresponding to the symbol rate, and the first optical path at a symbol rate other than the specific symbol rate. The optical phase modulation evaluation apparatus according to claim 1, wherein An optical phase delay device that is provided on any one of the first and second optical paths of the bit delay interferometer and can arbitrarily set a delay amount that can be changed by one period of the optical phase difference between the two optical paths. (4) and
The optical phase modulation evaluation apparatus according to any one of claims 1 to 6, further comprising phase control means (13) for setting a delay amount of the optical phase delay device.   The optical phase delay device is constituted by the second corner mirror, and can be set to an arbitrary delay amount by moving the second corner mirror in a direction parallel to the second optical path. The optical phase modulation evaluation apparatus according to claim 7.   The optical phase retarder is a parallel plate (4a) made of a transparent material having a thickness for giving a predetermined delay amount, and changes the incident angle of light to the parallel plate by rotating the parallel plate. The optical phase modulation evaluation apparatus according to claim 7, wherein an arbitrary delay amount can be set. The optical phase retarder is a pair of _two parallel plates (4b ₁ , 4b ₂ ) made of a transparent material having a thickness for giving a predetermined delay amount, and the pair of parallel plates is incident on the light. Arranged in a square shape so that the angle and the exit angle are substantially equal, and by rotating at least one of the two parallel plates to change the incident angle of light to the parallel plates The optical phase modulation evaluation apparatus according to claim 7, wherein the delay amount can be set.   In order for the bit delay interferometer to give a relative delay time to the two light intensity conversion signals output from the beam splitter, one of the optical paths through which the two light intensity conversion signals pass 11. The optical phase modulation evaluation apparatus according to claim 1, further comprising an optical output signal delay device (5) for changing the length.

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