JP2008292937A - Light pulse pattern generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light pulse pattern generator that can generate an ultrafast light random pattern having various signal forms, periods, bit rates and patterns without using a pulse pattern generator and a signal processor in an electric region or a long optical delay line. <P>SOLUTION: A beam from a pulse light source ( CW (continuous wave) light source may be used) is modulated by a light intensity modulator 21 and divided into two beams by an optical light tap 22. One beam is divided into two beams by a first optical coupler 23-1; the two beams are routed through respective variable or fixed optical delay lines 24 having different delay amounts from each other and having lengths of about only several to several hundreds times of a bit rate length; and then multiplexed by a second optical coupler 23-2. The multiplexed optical signal is subjected to photoelectric conversion by a light receiving device 26; and the electric signal is used to drive the light intensity modulator 32 to extract the other output of the optical tap 22 as an output signal. Thus, a function of delay and photo-electric hybrid exclusive OR in an optical region, and as a result, an optical linear feedback shift register is achieved and a ultrafast light random pattern over 40 Gb/s can be obtained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In particular, in the field of optical communication, the present invention relates to generation of an optical random pulse pattern sequence for evaluation (code error rate, eye pattern measurement) of various optical devices, generation of an optical label pulse sequence for optical packet signals, optical CDMA (Code Division Multiple The present invention relates to an optical pulse pattern generator capable of generating a random signal for (Access: code division multiple access).

When evaluating an optical communication system and an optical communication device by measuring a signal error rate, a sufficiently long random pulse pattern sequence having a variable period of up to about 2 ³¹ -1 bits is essential. When transmitting an optical packet signal, it is necessary to add a label pulse train in addition to the data signal (payload). Furthermore, in optical CDMA, it is necessary to modulate a data signal with a random pattern.

  As a high-speed optical pulse pattern generator used for such an application, one having a configuration shown in FIG. 1A has been generally used (Non-Patent Documents 1 and 2). In order to generate a high-speed optical pulse pattern of 40 Gb / s or more for optical communication, it is difficult to generate a signal from a single electronic circuit due to speed limitation. For this reason, the following operation is performed in the conventional apparatus shown in FIG.

Four types of 10 Gb / s random pulse pattern electric signals that are easy to generate are generated by the electric pulse pattern signal generation circuit 1. The timing control of these four kinds of signals is performed, and after delaying the timing by 1/4 period of 2 ^Q −1 (Q: integer of 1 or more) bits, which is one period of a desired random signal, electric multiplexing is performed. Then, time multiplexing is performed using the conversion circuit 3 and a desired signal is output from the electric signal output unit 4. By driving the light intensity modulator 7 using the electrical signal output from the electrical signal output unit 4, the laser light supplied from the laser 5 was modulated to obtain an optical random pulse pattern output of 40 Gb / s. . As described above, the electrical pulse pattern signal generation circuit 1 performs the delay by shifting the timing by ¼ period because of the randomness of the actual line based on the ITU (International Telecommunication Union) standard. This is to generate a close random pattern.

  Further, conventionally, an ultrahigh-speed optical pulse pattern exceeding 40 Gb / s has a configuration shown in FIG. 1B (Non-patent Document 3). In a signal speed region exceeding 40 Gb / s, it is difficult to generate a basic electric signal and perform timing control before multiplexing depending on the configuration of FIG. Therefore, for example, in order to generate a 160 Gb / s ultrafast optical pulse pattern signal, the conventional apparatus shown in FIG. 1B performs the following operation.

  A basic 40 Gb / s optical signal is generated by an optical random pulse pattern signal generation circuit 9 having the same configuration as that shown in FIG. 1A, and then the 40 Gb / s optical signal is output by an optical splitter 11. By using the optical delay lines 12-1 to 12-4 and the optical combiner 13 for the optical signal divided into four equal parts, a delay time multiplexing of 1/4 of a desired random signal period is performed. Then, a desired 160 Gb / s ultrafast optical pulse pattern signal was obtained from the optical signal output unit 14.

Kagawa, “Code Error Rate Measuring Device (Bit Error Rate Measuring Device),” Optical Communication Technology Handbook, pp.394-396, 2002 R.J.S. Pedersen, B.F. Jorgensen, M. Nissov, and H. Yongqi, “10 Gbit / s repeaterless transmission over 250 km standard fiber,” Electronics Letters, vol. 32, no. 23, pp. 2155-2156, 1996, E. Yamada, E. Yoshida, T. Kitoh, and M. Nakazawa, “Generation of terabit per second optical data pulse train,” Electronics Letters, vol.31, no.16, pp.1342-1344, 1995.

When generating a random pulsed optical signal having a sufficiently long period (2 ³¹ -1 bits) necessary for optical communication and compliant with the ITU standard of 40 Gb / s or more, as shown in FIG. In the conventional method shown in the drawing, it is necessary to generate a plurality of 10 Gb / s random pulse pattern electrical signals and perform time multiplexing after adjusting the timing, which complicates the apparatus and increases the cost. In addition, since the main parts other than the light intensity modulation are all processed in the electrical domain, it is difficult to generate a signal exceeding 40 Gb / s.

  On the other hand, when a 40 Gb / s random pulse optical signal compliant with, for example, the ITU standard is generated by the conventional method shown in FIG. 1B, the optical delay lines 12-2, 12-3, 12-4 are optical Delay line length differences of ˜2684 km, ˜5369 km, and ˜8053 km are required for the delay line 12-1, respectively, and the delay line length difference needs to be adjusted with an accuracy of ˜5 mm. Both the delay line length difference and the length fitting accuracy are inversely proportional to the required bit rate. Further, these optical delay lines 12-1 to 12-4 are fixed delay lines, and therefore do not support generation of variable period patterns. Considering the loss (˜0.2 dB / km) of the optical fiber that can be used as these optical delay lines, length adjustment accuracy, and cost, the conventional method shown in FIG. is there.

  The present invention has been made in view of the above-described prior art, and the object thereof is various without using a pulse pattern generator and a signal processor in the electrical domain, a long optical delay line, and the like. To provide an optical pulse pattern generator capable of generating an ultrafast optical random pattern having a signal form (RZ (Return-to-Zero), NRZ (Non Return-to-Zero), etc.), period, bit rate, and pattern. It is in.

  In order to achieve the above object, an optical pulse pattern generator according to a first aspect of the present invention includes a pulse light source that generates an optical pulse signal, an optical intensity modulator that modulates the optical pulse signal in accordance with an electric drive signal, and An optical tap that bisects the optical pulse signal modulated by the optical intensity modulator, a first optical coupler that bisects an optical pulse signal of one output of the optical tap, and the first optical coupler. The variable and fixed first and second optical delay lines having different delay amounts for respectively delaying the optical pulse signals of the first and second optical delay signals and the two optical output signals delayed by the first and second optical delay lines are multiplexed. The second optical coupler and the logical output of the two optical output signals obtained by combining with the second optical coupler are photoelectrically converted, and the logical output of the converted electric signal is used as the electric drive signal. A light receiver for supplying to the light intensity modulator; Characterized by comprising an output unit to retrieve the other output of the-up as an output signal.

  In order to achieve the above object, an optical pulse pattern generator according to a second aspect of the present invention includes a pulse light source that generates an optical pulse signal, and an optical intensity modulation that modulates the optical pulse signal according to an electric drive signal. , An optical tap that bisects the optical pulse signal modulated by the optical intensity modulator, an optical coupler that bisects an optical pulse signal output from one of the optical taps, and an optical pulse signal from the optical coupler The first and second optical delay lines having different delay amounts and the two optical output signals delayed by the first and second optical delay lines are respectively photoelectrically converted, and the 2 A balanced light receiver that obtains a difference between the two electrical signals as a logical output of two optical output signals and supplies the obtained logical output to the light intensity modulator as the electrical drive signal; and the other output of the optical tap As the output signal Characterized by comprising an output unit to retrieve.

  Here, the light intensity modulator has a Mach-Zehnder interferometer structure, and when there is no input of the electric drive signal, the output light intensity is close to the minimum value (or the maximum value), and It can be assumed that the electric bias is set so that the output light intensity is close to the maximum value (or the minimum value) when the electric drive signal is input.

  A second optical tap is used as a first optical tap, and is connected between the pulse light source and the light intensity modulator separately from the first optical tap to bisect the output of the pulse light source. Of the second optical tap, a third optical coupler that causes the tap output light of the second optical tap and the output light of the first optical tap to interfere with each other, and the output unit is replaced with the third optical coupler. An output unit that extracts one output as an output signal may be further included.

  Further, it can be assumed that a direct current (CW: Continuous Wave) light source is disposed at the position of the pulse light source instead of the pulse light source.

  In addition, an optical gate element connected to the output unit may be further provided.

  Each of the first and second optical delay lines is a variable optical delay line, and each of K delay line pairs having different lengths (K is an integer of 1 or more) and delay line pairs at both ends. And a total of K + 1 symmetrical Mach-Zehnder interferometers each having a phase adjustment unit on at least one arm.

Alternatively, each of the first and second optical delay lines is a variable optical delay line, and the difference in length is ΔL, 2ΔL, 4ΔL,..., 2 ^P−2 ΔL, 2 ^P−1. A total of P + 1 symmetrical Mach-Zehnder interferometers each having a phase adjustment unit on at least one arm between P delay line pairs of ΔL (P is an integer of 1 or more) and before and after a delay line pair at both ends. It can be assumed to be of a connected configuration.

  In the present invention, as described above, the output of the pulse light source is variable or fixed having a length of about several times to several hundred times the bit rate length through the light intensity modulator, the optical tap, and the optical coupler. Two optical delay lines are connected, and the electric signal obtained from the output of the optical delay line via the light receiver is fed back as a driving electric signal for optical intensity modulation. An exclusive OR function is realized, and an optical linear feedback shift register is realized with parameters sufficiently realizable by the current manufacturing technology. As a result, according to the present invention, an optical pulse pattern generator capable of generating an ultrafast optical random pattern having various signal forms, periods, bit rates, and patterns only by adjusting the length of the optical delay line is provided. This can be easily realized without using a pulse pattern generator and signal processor in a region, a long optical delay line, and the like.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 2 shows a configuration example of the optical pulse pattern generator in the first embodiment of the present invention. In this optical pulse pattern generator, the pulse light source 20, the light intensity modulator 21, the optical tap 22, the optical couplers 23-1, 23-2, the variable delay lines 24-1, 24-2, the phase adjusting unit 25, and the light reception The device 26 is connected to the substrate 29 by an integration technique using optical wirings 27-1 to 27-3 (indicated by a solid line) and electrical wiring 28 (indicated by an alternate long and short dash line). Reference numeral 27-4 denotes an output unit.

  Among the above components 20 to 28, the optical tap 22, the optical couplers 23-1 and 23-2, the variable delay lines 24-1 and 24-2, the optical wirings 27-1 to 27-3, and the output unit 27- 4 is stable and has a low loss of ~ 0.01 dB / cm, and can be manufactured using a silica-based glass waveguide technology on a silicon or glass substrate 29 that can be precisely adjusted in length. it can. As the phase adjusting unit 25, a thin film heater of chromium or tantalum nitride (thermo-optic phase shifter, capable of precise phase adjustment of 0.01π or less; not shown) deposited on quartz glass can be used. As the electrical wiring 28, a gold wire deposited on quartz glass can be used.

Further, the optical tap 22, the optical couplers 23-1, 23-2, the variable delay lines 24-1, 24-2, the optical wirings 27-1 to 27-3, and the output unit 27-4 are connected to a polymer waveguide, LiNbO. ₃ (LN: lithium niobate), KTa _1-x Nb _x O ₃ (KTN: potassium tantalate niobate) and other ferroelectric waveguides, semiconductor waveguides, waveguides such as silicon waveguides, or these It is also possible to use a hybrid configuration using a plurality. In this case, the phase adjusting unit 25 is configured by using a thin film heater (thermo-optic effect) when the adjusted waveguide unit is formed of a polymer waveguide or a silicon waveguide, and the adjusted waveguide unit is strengthened. In the case of a dielectric waveguide or a semiconductor waveguide, an electrode (electro-optic effect) is used. Furthermore, it is of course possible to connect 27-1 to 27-3 with optical fibers, 28 with a coaxial cable, and other devices with individual devices using 27-1 to 27-3 and 28.

  The pulse light source 20 includes a semiconductor laser, an optical fiber mode-locked laser, a semiconductor gain switch light source, a CW (continuous wave oscillation) light source, and a light intensity modulator (an interferometer using an electro-optic effect of a ferroelectric material or a semiconductor material). A configuration in which a type modulator or a semiconductor EA (electroabsorption type) modulator) is combined can be used. The light intensity modulator 21 may be an interferometer type modulator using the electro-optic effect of a ferroelectric material or a semiconductor material, or a semiconductor EA modulator. The light receiver 26 can use a semiconductor element.

  Hereinafter, as a specific example of the present embodiment, the optical tap 22, the optical couplers 23-1, 23-2, the variable delay lines 24-1, 24-2, the optical wirings 27-1 to 27-3, and The output unit 27-4 is formed using a silica-based glass waveguide, and the other components will be described as being formed by hybrid integration or vapor deposition of devices of other materials on the silica-based glass waveguide.

Here, the light intensity modulator 21 uses a semiconductor EA modulator. The optical tap 22 and the optical couplers 23-1 and 23-2 are various by making two optical waveguides of several μm square approach each other on the order of several μm and adjusting the length (coupling length) of the adjacent parts. A directional coupler that achieves a high strength coupling rate is used. In order to make the description simple and clear, an example of generating a short random pulse pattern having a sequence length of 2 ⁴ −1 = 15 (period T1 = 15T, where T is a repetition period of the pulse light source 20) will be described.

The signal propagation time of one round of the loop from the light intensity modulator 21 via the first variable delay line 24-1 or the second variable delay line 24-2 and then returning to the light intensity modulator 21 via the electrical wiring 28 Also, ΔT ₁ = T and ΔT ₂ = 4T are set using the variable delay providing function of the variable delay lines 24-1 and 24-2. That is, the propagation time difference between the two variable delay lines 24-1 and 24-2 of the optical couplers 23-1 to 23-2 is 3T. By using such variable delay lines 24-1 and 24-2, it is possible to generate pulses having various sequence lengths and patterns with one element (optical pulse pattern generator). If only fixed pulse pattern generation is considered, the variable delay lines 24-1 and 24-2 are eliminated from the configuration of FIG. 2, and the optical wirings 27-1 and 27-2 are previously connected so that the signal propagation time is generated. It does not matter if the length is fixed. In this case, simplification of the configuration is achieved.

  FIG. 3 shows a configuration example of the variable delay lines 24-1 and 24-2 in FIG. As shown in FIG. 3, the variable delay line is formed on each arm of one of the input waveguides 30-1 and 30-2 on the thermo-optic phase shift thin film heater 31-1. ˜P + 1 (P: an integer of 1 or more) are individually arranged to form a plurality of symmetrical Mach-Zehnder interferometer type 2 × 2 optical switches 32-1 to P + 1, and each of these 2 × 2 optical switches 32-1 to P + 1. A pair of asymmetric arms 33a-1 to P, 33b-1 to P, and output waveguides 34-1 and 34-2 are connected to each other.

One of the input waveguides 30-1 and 30-2 and one of the output waveguides 34-1 and 34-2 are used as input / output units, respectively. The length difference ΔL _P between the asymmetric arm pairs 33a-1 to P, 33b- ₁ to ^P is set to ΔL _P = 2 ^P−1 ΔL ₁ in this configuration example. By changing the switching state of each of the 2 × 2 optical switches 32-1 to P + 1, the characteristics between the input waveguides 30-1 and 30-2 and the output waveguides 34-1 and 34-2 are set to 0 to (2 ^P -1) the range of [Delta] L _1, the relative delay of the variable can be a total of 2 ^P as can be realized with minimum configuration in [Delta] L ₁ increments. For example, at most P = 10, 1024 delay times can be set. Note that ΔL _P may be an arbitrary value, but the method of changing by two times as described above is the most efficient. Moreover, although increasing the [Delta] L _P from left to right in FIG. 3, this sequence may be arbitrary, increasing the [Delta] L _P from right to left, or order may of course be random.

  As the variable delay lines 24-1 and 24-2 in FIG. 2, for example, other configuration examples as shown in FIGS. 4 and 5 can be used.

  The variable delay line shown in FIG. 4 includes an input unit 40, an optical demultiplexer 41, fixed delay lines 42-1 to 42-Q (Q: an integer of 2 or more), 2 × 2 optical switches 43-1 to 43-Q. , Waveguides 44-1 to 44-Q, an optical multiplexer 45, and an output unit 46. In order to change the length of each fixed delay line 42-1 to 42-Q in advance and obtain a desired optical path length, only one of the 2 × 2 optical switches 43-1 to 43-Q is used. In the cross state, switching control is performed so that only one of the lights that have passed through the fixed delay lines 42-1 to 42-Q is guided to the optical multiplexer 45. The other light is not emitted to the corresponding waveguide 44 because the corresponding 2 × 2 optical switch 43 is in the bar state, and thus is not emitted from the output unit 46. In this way, the desired function of the variable delay line is realized.

  As is well known, the optical demultiplexer 41 and the optical multiplexer 45 are configured to cascade a star coupler, a multimode interference (MMI) coupler, and a 2 × 2 directional coupler in multiple stages, A configuration in which 2 × 2 symmetrical Mach-Zehnder interferometers are cascaded in multiple stages, a configuration in which Y branch waveguides are cascaded in multiple stages, or the like can be used.

  The variable delay line shown in FIG. 5 is a waveguide 50-1 to 50-R + 1 (R: integer greater than or equal to 2, using the left end of either 50-1 or 50-2 as an input unit), 2 × 2 optical switch 51-1 to 51-R, an optical multiplexer 52, and an output unit 53. When light enters from one waveguide 50-1 at the left end, in order to obtain a desired optical path length, only one of the 2 × 2 optical switches 51-1 to 51-R is set in a crossed state, The delay amount is adjusted by passing any one of the waveguides 50-2 to 50 -R + 1 to be switched, and switching control is performed so as to guide to the optical multiplexer 52. In this way, the desired function of the variable delay line is realized.

  Returning to FIG. 2 again, the operation of the optical pulse pattern generator of this embodiment will be described. The bias voltage of the light intensity modulator 21 is set so that the light intensity transmittance is maximized. When the intensity coupling ratio of the optical couplers 23-1 and 23-2 is set to 50%, the phase difference between the variable delay lines 24-2 and 24-1 is set to an integer multiple of 2π using the phase adjustment unit 25. In this case, the relative relationship of the light intensity between the two inputs A and B to the optical coupler 23-2 and the output C of the optical coupler 23-2 is given in Table 1 below.

  When the two inputs A and B to the optical coupler 23-2 are both 1, all light is output to an arm different from the optical wiring 27-3 due to interference of light waves. From Table 1, it can be seen that the two inputs A and B and the output C logically have an exclusive OR relationship represented by the following Expression 1.

  FIG. 6A is a characteristic diagram showing the relationship between the voltage of the electric signal input as the control signal and the light intensity of the output optical signal when the light intensity modulator 21 is a Mach-Zehnder type modulator. (B) is a characteristic diagram showing the relationship between the voltage of the electrical signal input as the control signal and the light intensity of the output optical signal when the light intensity modulator 21 is an EA modulator.

  The optical wiring 27-3 is subjected to O / E (photoelectric) conversion by the light receiver 26, and the electrical output is used as a control signal. In the case of driving 21, the intensity of the repetitive optical signal pulse of the optical pulse light source 20 is negated by the above equation 1 as shown in the following equation 2 through light modulation using an electrical signal (see FIG. 6). The output is reflected.

  Therefore, as an optical output to be output from the output unit 27-4 to the outside of the apparatus, as shown in FIG. 7B, an M (Maximum Length Shift Register) sequence (more precisely, M) It can be seen that the series 0 and 1 are inverted). 7A shows the output of the optical pulse light source 20, and FIG. 7B shows the optical random pulse pattern generated by the optical pulse pattern generator of the present invention.

Further, the light intensity modulator 21 when ΔT ₁ = 3T and ΔT ₂ = 4T are set (therefore, the propagation time difference between the two delay lines from the optical coupler 23-1 to the optical coupler 23-2 is T). The state of the optical pulse of the output unit 27-4 is shown in FIG. Here, FIG. 8A shows the output of the optical pulse light source 20, and FIG. 8B shows the optical random pulse pattern generated by the optical pulse pattern generator of the present invention.

  In the same manner, an M sequence having a sequence length of 15 (more precisely, an inverted version of 0 and 1 of the M sequence) can be realized. Thus, according to the optical pulse pattern generator of this embodiment, it can be seen that various sequences can be easily generated by adjusting the delay of the variable delay lines 24-1 and 24-2. Further, according to the optical pulse pattern generator of the present embodiment, a variable random pulse pattern sequence having a variable bit rate can be generated in the same manner.

For the sake of simplicity, an example of generating a pulse pattern with a sequence length of 15 has been shown. However, generation of a pulse pattern with a long sequence length such as 2 ²³ -1 and 2 ³¹ -1 is also possible with the variable delay line 24- This can be achieved only by setting 1,24-2 to several to several tens of times the delay corresponding to 1-bit time slot time (in the case of 160 Gb / s, a delay of 1.25 mm).

  Regarding the optical pulse light source 21 and the light receiver 26, those corresponding to a band of 40 Gb / s are commercially available, and those of a band higher than that of the order of 100 Gb / s are also realized in the research and development stage. The combination of an EA modulator and a single-running carrier photodiode (Uni-Traveling-Carrier Photodiode; UTC-PD) is particularly effective for speeding up. An electrical amplifier (not shown) is disposed in the electrical wiring 28 as necessary, but the light intensity modulator 21 corresponding to 40 Gb / s is also commercially available. Since the drive voltage of the light intensity modulator 21 is reduced to 1 V or less, the requirements regarding the gain of the electric amplifier are relaxed. In any case, since the functions of the light intensity modulator 21, the light receiver 26, and the electric amplifier are simpler than those of an electric logic circuit, it is easy to increase the bandwidth.

(Second Embodiment)
FIG. 9 shows a configuration example of an optical pulse pattern generator according to the second embodiment of the present invention. In this optical pulse pattern generator, a pulse light source 60, an optical intensity modulator 61, an optical tap 62, an optical coupler 63, variable delay lines 64-1, 64-2 and a balance type light receiver 65 are combined with an optical wiring 66-1. ˜66-3 (indicated by a solid line) and electrical wiring 67 (indicated by a one-dot chain line) are connected to the substrate 68 by an integration technique. Reference numeral 66-3 denotes an output unit. The balanced light receiver 65 outputs a difference between electrical signals obtained by photoelectrically converting signal light from the two outputs of the variable delay lines 64-1 and 64-2.

  A Mach-Zehnder type modulator is used as the light intensity modulator 61, and the bias voltage is set so that the light intensity transmittance is maximized. When the coupling rate of the optical coupler 63 is set to 50%, two optical input intensities D (variable delay line 64-1 side) and E (variable delay line 64-2 side) to the balanced light receiver 65, and this The relative relationship with the electrical output amplitude F of the balanced light receiver 65 is given in Table 2 below.

  From Table 2, it can be seen that when the sign is ignored, the input signal strengths D and E and the output signal amplitude F logically have an exclusive OR relationship represented by the following Expression 3.

  FIG. 10 is a diagram showing an operation when a Mach-Zehnder optical intensity modulator using an electric signal is used as the optical intensity modulator 61. The voltage (amplitude) of the electric signal input as the control signal and the output optical signal The relationship of the light intensity is shown. As shown in FIG. 10, a light intensity modulator using the electrical output as a control signal so that the transmittance is minimized when the positive and negative electrical signals are output on the electrical wiring 67 output from the balanced light receiver 65. 61 is driven. As a result, the negative output of the above equation 3 is reflected in the intensity of the repetitive optical signal pulse of the pulse light source 60 as shown in the following equation 4.

A loop that returns from the light intensity modulator 61 to the light intensity modulator 61 via the first variable delay line 64-1 or the second variable delay line 64-2 and the balanced light receiver 65 and the electrical wiring 67. When the signal propagation time of one round is set to ΔT ₁ = T and ΔT ₂ = 4T using the variable delay adding function of the variable delay lines 64-1 and 64-2, respectively (therefore, from the optical coupler 63 to the balanced type) The propagation time difference between the two delay lines up to the light receiver 65 is 3T), and the optical output of the output unit 66-3 is the M series of the sequence length 15 shown in FIG. Inverted series 0 and 1) can be realized.

Further, when ΔT ₁ = 3T and ΔT ₂ = 4T are set (therefore, the propagation time difference between the two delay lines from the optical coupler 63 to the balanced light receiver 65 is T), the above-described (b) of FIG. ) Of a different sequence length 15 shown in FIG. 5 (to be precise, one obtained by inverting 0 and 1 of the M sequence). As described above, it can be seen that, similarly to the configuration of FIG. 2, the configuration of FIG. 9 can easily generate various sequences.

(Third embodiment)
FIG. 11 shows a configuration example of an optical pulse pattern generator in the third embodiment of the present invention. In this optical pulse pattern generator, a pulse light source 70, an optical intensity modulator 71, optical taps 72-1, 72-2, optical couplers 73-1-73-3, variable delay lines 74-1, 74-2, phase The adjusting units 75-1 and 75-2 and the light receiver 76 are integrated on the substrate 79 by using the optical wirings 77-1 to 77-5 (displayed by solid lines) and the electrical wiring 78 (displayed by alternate long and short dash lines). Connected by. Reference numeral 77-6 denotes an output unit.

  A second optical tap 72-2 is connected between the pulse light source 70 and the light intensity modulator 71, and a third optical coupler 73 is connected to the output of the first optical tap 72-1 via the optical wiring 77-4. 3 is connected, and the second optical tap 72-2 and the third optical coupler 73-3 are connected via the second phase adjusting unit 75-2 and the optical wiring 77-5. Other configurations are the same as those in FIG.

  The setting of the light intensity modulator 71 is the same as that of the first embodiment of FIG. Using the optical taps 72-1 and 72-2, the light intensity in the optical wirings 77-4 and 77-5 is adjusted equally, and using the second phase adjustment unit 75-2, the optical wirings 77-4 and 77-5 are adjusted. Adjust the phase difference of light at.

  As the third optical coupler 73-3, a two-waveguide proximity type directional coupler (3 dB directional coupler) having a strength coupling ratio of 50% was used, and the phase difference was set to π / 2 + Sπ (S: integer). In this case, the relative relationship between the light intensities (G, H, and I, respectively) of the optical wirings 77-4 and 77-5 and the output unit 77-6 is given in Table 3 below, considering light wave interference. .

H is always 1. At this time, there is a negative relationship between G and I as shown in the following formula 5.

  Therefore, by using the configuration of FIG. 11, the negative output shown in FIG. 7B and FIG. 8B can be obtained from the output unit 77-6, and the output is inverted. No M sequence can be obtained.

A loop of a loop returning from the light intensity modulator 71 to the light intensity modulator 71 via the first variable delay line 74-1 or the second variable delay line 74-2 and the light receiver 76 and the electric wiring 78. The signal propagation times are set to ΔT ₁ = T and ΔT ₂ = 4T using the variable delay providing function of the variable delay lines 74-1 and 74-2, respectively (therefore, the optical coupler 73-1 to the optical coupler 73 are set). FIG. 12 shows a state of optical output at the output unit 77-6 in the case where the propagation time difference between the two delay lines up to −2 is 3T). 12A shows the output of the optical pulse light source 70, and FIG. 12B shows the optical random pulse pattern of the output of the output unit 77-6. Comparing the pulse pattern shown in FIG. 12B with the pulse pattern shown in FIG. 7B, it can be seen that the inverted output shown in FIG. 7B is obtained in this embodiment.

  The intensity branching ratio adjustment of the optical taps 72-1 and 72-2 and the optical couplers 73-1 to 73-3 using a directional coupler changes the proximity waveguide length at the time of fabrication in the case of the waveguide proximity type. Can be achieved. If thermal quenching and annealing are used for the directional coupler, the branching ratio can be adjusted after fabrication. When a symmetric Mach-Zehnder interferometer is used as the directional coupler of the optical taps 72-1, 72-2 and the optical couplers 73-1 to 73-3, the optical variable using the phase adjustment of the interferometer arm. Using the attenuation function, the branching ratio can be adjusted to an arbitrary value.

(Fourth embodiment)
FIG. 13 shows a configuration example of an optical pulse pattern generator in the fourth embodiment of the present invention. In this optical pulse pattern generator, a pulse light source 80, an optical intensity modulator 81, optical taps 82-1 and 82-2, optical couplers 83-1 and 83-2, variable delay lines 84-1 and 84-2, a balance are provided. The type light receiver 85 and the phase adjusting unit 86 are connected to the substrate 89 using an integration technique via optical wirings 87-1 to 87-4 (indicated by solid lines) and electrical wiring 88 (indicated by dashed lines). Has been. Reference numeral 87-5 denotes an output unit.

  A second optical tap 82-2 is connected between the pulse light source 80 and the light intensity modulator 81, and the second optical coupler 83 is connected to the output of the first optical tap 82-1 via the optical wiring 87-3. -2 is connected, and the second optical tap 82-2 and the second optical coupler 83-2 are connected via the phase adjusting unit 86 and the optical wiring 87-4. The other configuration is the same as the configuration of FIG. This configuration corresponds to a configuration in which the phase adjusting unit 75-1, the optical wiring 77-3, the optical coupler 73-2, and the light receiver 76 in FIG. Therefore, the same principle as in FIG. 11 is applied to this embodiment.

  With the above configuration, when the setting of the light intensity modulator 81 is the same as that of the configuration of FIG. 9, an M sequence in which the output is not inverted is obtained from the output unit 87-5 by the same principle as in FIG. 11 described above. Can do.

(Fifth embodiment)
FIG. 14 shows a configuration example of an optical pulse pattern generator in the fifth embodiment of the present invention. This optical pulse pattern generator is obtained by replacing the pulse light source of FIG. 2 with a CW light source. That is, in this optical pulse pattern generator, a CW light source 90, an optical intensity modulator 91, an optical tap 92, optical couplers 93-1, 93-2, variable delay lines 94-1 and 94-2, a phase adjusting unit 95, A light receiver 96 is connected to the substrate 99 by using an integration technique via optical wirings 97-1 to 97-3 (indicated by solid lines) and electrical wiring 98 (indicated by dashed-dotted lines). Reference numeral 97-4 denotes an output unit. As the CW light source 90, a known CW light source such as an optical fiber laser, an SLD (Super Luminescent Diode), and an LED (light emitting diode) can be used in addition to a normal semiconductor laser.

The configuration shown in FIG. 14 has a linear feedback shift register configuration as in FIG. 2, and can generate a random pulse pattern. When the light intensity modulator 91 performs the step function switching operation shown in FIG. 15A, the light intensity modulator 91 receives light via the variable delay line 94-1 or the variable delay line 94-2. The signal propagation time of one round of the loop returning to the light intensity modulator 91 via the circuit 96 and the electrical wiring 98 is also expressed as ΔT ₁ = T using the variable delay providing function of the variable delay lines 94-1 and 94-2, respectively. , ΔT ₂ = 4T (therefore, the propagation time difference between the two delay lines from the optical coupler 93-1 to the optical coupler 93-2 is 3T). In the case of this configuration, since the CW light generated from the CW light source 90 is incident on the light intensity modulator 91, an NRZ format random pulse shown in FIG. 15B is obtained from the output unit 97-4.

  Since the NRZ signal cannot be time-delay multiplexed in the optical domain, there is no report on the generation of an NRZ optical random pulse pattern signal exceeding 40 Gb / s. Therefore, the configuration of FIG. 14 is currently the only method capable of generating an ultrafast NRZ optical random pulse pattern signal.

(Sixth embodiment)
FIG. 16 shows a configuration example of an optical pulse pattern generator in the sixth embodiment of the present invention. In this optical pulse pattern generator, an optical gate element 129 is arranged in the output post stage 27-4 of the optical pulse pattern generator having the configuration shown in FIG. 2, and 127-5 is used as an output section.

  The optical gate element 129 may be disposed at the subsequent stage of the configuration of FIG. 9, FIG. 11, FIG. 13, or FIG. As the optical gate element 129, a ferroelectric or polymer light intensity modulator, a semiconductor EA modulator, a gate function of a semiconductor laser amplifier (SOA), or the like can be used.

  In the configuration of FIG. 2, FIG. 9, FIG. 11, FIG. 13 or FIG. 14, random pulse patterns are generated continuously. However, when the optical packet signal 140, which is a burst signal shown in FIG. 17A, is routed using the optical router 145 as shown in FIG. 17B, an optical label pulse train of only one period is used. is required. Therefore, in the optical pulse pattern generator of FIG. 16, the optical gate element 129 temporally extracts a random pulse pattern sequence of only one cycle as the pulse sequence for the optical label, and outputs the extracted random pulse pattern sequence of only one cycle. It is set to output from the unit 127-5.

  The optical packet signal generating device 143 shown in FIG. 17B multiplexes the label pulse generated by the optical pulse pattern generator of FIG. Is generated.

  The optical packet signal 140 generated by the optical packet signal generation device 143 is input to the optical router 145 through the optical fiber 144. The optical label signal 141 (see FIG. 17A) of the optical packet signal 140 is extracted at the optical tap 149, sent to the light receiver 151 via the optical connection unit 147-4, and converted into an electrical signal. . At the same time, the optical packet signal 140 is supplied to the optical switch 150 via the optical connection unit 147-3. The label signal converted into the electrical signal is determined by the label signal determination device 153, and the determination signal is supplied to the optical switch 150 via the electrical connection unit 152-2. The optical switch 150 selects a distribution destination of the optical packet signal 140 based on the determination signal, and distributes the optical packet signal 140 through at least one of the optical fibers 146-1 to 146-U. U is an integer of 2 or more.

(Seventh embodiment)
FIG. 18 shows a configuration example of an error rate measuring apparatus using the optical pulse pattern generator according to the present invention shown in FIG. 2, FIG. 9, FIG. 11, FIG.

  The error rate measuring apparatus shown in FIG. 18 uses an optical sampling oscilloscope 103 that allows a high-speed pulse pattern generated by the optical pulse pattern generator 100 of the present invention to enter the device under test 102 and measure the high-speed optical pulse. Perform an evaluation. Reference numerals 101-1 and 102-2 denote optical connection units.

(Eighth embodiment)
FIG. 19 shows a configuration example of an optical CDMA transmitter using the optical pulse pattern generator according to the present invention shown in FIG. 2, FIG. 9, FIG. 11, FIG.

  The optical CDMA transmitter of FIG. 19 uses the high-speed pulse pattern generated by the optical pulse pattern generator 110 of the present invention as a code for optical CDMA. More specifically, the high-speed pulse pattern generated by the optical pulse pattern generator 110 is input to the optical intensity modulator 112 via the optical connection unit 111-1. The light intensity modulator 112 uses the electrical data signal 114 in which one cycle of the code corresponds to one time slot, and performs intensity modulation using the high-speed pulse pattern as a code for optical CDMA in synchronization. Is encoded. The generated data signal is transmitted to the optical transmission line 113 via the optical connection unit 111-2. Reference numeral 115 denotes an electrical connection portion.

(Other embodiments)
In the above description, the number of feedback connections for feedback is 1, but of course, it may be 2 or more.

  Although only the optical output has been described above, it is of course possible to tap the signal obtained by O / E conversion of the optical output or the signal of the electrical wiring and use it as a pulse pattern generator for the electrical signal.

  In the above, the preferred embodiment of the present invention has been described by way of example. However, the embodiment of the present invention is not limited to the above-described example, and the constituent members thereof are within the scope of the claims. Various modifications such as replacement, change, addition, increase / decrease in number, change in shape design, etc. are all included in the embodiments of the present invention. In addition, the present invention may be applied to a system composed of a plurality of devices, or may be applied to an apparatus composed of one device.

(A) And (b) is a block diagram which shows the structure of the conventional optical pulse pattern generator, respectively. It is a block diagram which shows the structure of the optical pulse pattern generator in the 1st Embodiment of this invention. FIG. 3 is a schematic diagram illustrating a configuration of a variable optical delay line in FIG. 2. FIG. 3 is a block diagram showing another configuration of the variable optical delay line in FIG. 2. FIG. 10 is a block diagram showing still another configuration of the variable optical delay line in FIG. 2. 2A and 2B show the operation of the light intensity modulator using the electrical signal of FIG. 2, where FIG. 2A shows a case where a Mach-Zehnder type modulator is used as the light intensity modulator, and FIG. 2B shows an EA modulator as the light intensity modulator. It is a characteristic view which shows the relationship between the voltage of an input electrical signal, and the optical intensity of an output optical signal when used. (A) is an output of the pulse light source of FIG. 2, and (b) is a timing diagram showing an optical random pulse pattern generated by the optical pulse pattern generator of the present invention of FIG. When the signal propagation time for one round of the loop is set to another value, (a) is an output of the pulse light source of FIG. 2, and (b) is an optical random pattern generated by the optical pulse pattern generator of the present invention of FIG. It is a timing diagram which shows a pulse pattern. It is a block diagram which shows the structure of the optical pulse pattern generator in the 2nd Embodiment of this invention. FIG. 10 is a characteristic diagram showing an operation state when a Mach-Zehnder optical intensity modulator using an electric signal is used as the optical intensity modulator of FIG. 9 and showing the relationship between the voltage of the input electric signal and the optical intensity of the output optical signal. . It is a block diagram which shows the structure of the optical pulse pattern generator in the 3rd Embodiment of this invention. (A) is an output of the pulse light source of FIG. 11, (b) is a timing diagram showing an optical random pulse pattern generated by the optical pulse pattern generator of the present invention of FIG. It is a block diagram which shows the structure of the optical pulse pattern generator in the 4th Embodiment of this invention. It is a block diagram which shows the structure of the optical pulse pattern generator in the 5th Embodiment of this invention. (A) is the output of the CW light source of FIG. 14, (b) is a timing diagram showing the optical random pulse pattern generated by the optical pulse pattern generator of the present invention of FIG. It is a block diagram which shows the structure of the optical pulse pattern generator in the 6th Embodiment of this invention. (A) is a figure which shows the pulse train for optical packets produced | generated by the optical packet signal generation apparatus using the optical pulse pattern generator of FIG. 16, (b) is the combination of the optical packet signal generation apparatus and an optical router. It is a block diagram which shows a structure. It is a block diagram which shows the structure of the signal error rate measurement system using the optical pulse pattern generator of this invention as the 7th Embodiment of this invention. FIG. 10 is a block diagram showing a configuration of an optical CDMA transmitter using the optical pulse pattern generator of the present invention as an eighth embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrical pulse pattern signal generation circuit 2 Electrical connection part 3 Electrical multiplexing circuit 4 Electrical output 5 Laser 6 Optical connection part 7 Optical intensity modulator 8 Optical output part 9 Optical random pulse pattern generator 10 Optical connection part 11 Optical splitter 12 Light Delay line 13 Optical combiner 14 Optical output 20, 60, 70, 80, 120 Light source 21, 61, 71, 81, 91, 121 Optical intensity modulator 22, 62, 72, 82, 92, 122 Optical tap 23, 63 , 73, 83, 93, 123 Optical coupler 24, 64, 74, 84, 94, 124 Variable delay line 25, 75, 86, 95, 125 Phase adjustment unit 26, 76, 96, 126 Receiver 27, 66, 77 , 87, 97, 127 Optical wiring 28, 67, 78, 88, 98, 128 Electrical wiring 29, 68, 79, 89, 99, 130 Substrate 30 Input waveguide 31 Thermo-optic phase shift thin film heater 32 Symmetric Mach-Zehnder interferometer type 2 × 2 optical switch 33 Asymmetric arm pair 34 Output waveguide 40 Input section 41 Optical demultiplexer 42 Fixed delay line 43 2 × 2 optical switch 44 Waveguide 45 Optical coupling Wave generator 46 Output section 50 Waveguide 51 2 × 2 optical switch 52 Optical multiplexer 53 Output section 65, 85 Balanced light receiver 90 CW light source 100 Optical pulse pattern generator 101 Optical connection section 102 Device under test 103 Light of the present invention Sampling oscilloscope 110 Optical pulse pattern generator of the present invention 111 Optical connection unit 112 Optical intensity modulator 113 Optical transmission line 114 Electrical data signal 115 Electrical connection unit 129 Optical gate element 140 Optical packet signal 141 Optical label signal 142 Optical payload signal (optical Data signal)
143 Optical packet signal generator 144 Optical fiber 145 Optical router 146 Optical fiber 147 Optical connection unit 148 Optical gate element 149 Optical tap 150 Optical switch 151 Optical receiver 152 Electrical connection unit 153 Label signal determination device

Claims (8)

A pulse light source for generating an optical pulse signal;
A light intensity modulator that modulates the optical pulse signal according to an electric drive signal;
An optical tap that bisects the optical pulse signal modulated by the optical intensity modulator;
A first optical coupler that bisects an optical pulse signal at one output of the optical tap;
Variable or fixed first and second optical delay lines having different delay amounts for respectively delaying the optical pulse signals from the first optical coupler;
A second optical coupler for combining two optical output signals delayed by the first and second optical delay lines;
The logical output of the two optical output signals obtained by combining by the second optical coupler is photoelectrically converted, and the logical output of the converted electric signal is supplied to the optical intensity modulator as the electric drive signal. A receiver,
An optical pulse pattern generator, comprising: an output unit that extracts the other output of the optical tap as an output signal. A pulse light source for generating an optical pulse signal;
A light intensity modulator that modulates the optical pulse signal according to an electric drive signal;
An optical tap that bisects the optical pulse signal modulated by the optical intensity modulator;
An optical coupler that bisects an optical pulse signal at one output of the optical tap;
Variable or fixed first and second optical delay lines having different delay amounts for delaying optical pulse signals from the optical coupler,
The two optical output signals delayed by the first and second optical delay lines are respectively photoelectrically converted to obtain a difference between the two electrical signals as a logical output of the two optical output signals, and the obtained logical output A balance type light receiver that supplies the light intensity modulator as an electric drive signal;
An optical pulse pattern generator, comprising: an output unit that extracts the other output of the optical tap as an output signal.   The light intensity modulator has a Mach-Zehnder interferometer structure, and when there is no input of the electric drive signal, the output light intensity is close to the minimum value (or the maximum value) and the electric drive 3. The optical pulse pattern generator according to claim 2, wherein the electric bias is set so that the output light intensity is in the vicinity of the maximum value (or the minimum value) when a signal is input. Second light that is connected between the pulse light source and the light intensity modulator and divides the output of the pulse light source into two separately from the first light tap, wherein the light tap is a first light tap. Tap,
A third optical coupler that causes interference between the tap output light of the second optical tap and the output light of the first optical tap;
4. The optical pulse pattern generator according to claim 1, further comprising an output unit that replaces the output unit and extracts one output of the third optical coupler as an output signal. 5. .   5. The optical pulse pattern generator according to claim 1, wherein a direct current (CW: Continuous Wave) light source is disposed at a position of the pulse light source in place of the pulse light source.   The optical pulse pattern generator according to claim 1, further comprising an optical gate element connected to the output unit.   The first and second optical delay lines are variable optical delay lines, respectively, and between K delay line pairs having different lengths (K is an integer of 1 or more) and before and after the delay line pairs at both ends. 7. The optical pulse pattern according to claim 1, wherein a plurality of K + 1 symmetrical Mach-Zehnder interferometers each having a phase adjustment unit on at least one arm are connected. Generator. The first and second optical delay lines are variable optical delay lines, and the length difference is ΔL, 2ΔL, 4ΔL,..., 2 ^P−2 ΔL, 2 ^P−1 ΔL. A configuration in which a total of P + 1 symmetric Mach-Zehnder interferometers each having a phase adjustment unit on at least one arm are connected between P delay lines (P is an integer of 1 or more) and before and after the delay line pairs at both ends. The optical pulse pattern generator according to any one of claims 1 to 6, wherein

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