JP6059589B2 - Optical modulator and optical modulator using the same - Google Patents

Description

  The present invention relates to an optical modulator for generating an optical signal and an optical modulation device using the optical modulator, and more particularly to an optical modulator for generating and modulating a plurality of subcarriers and an optical modulation device using the optical modulator.

  With vigorous demand for communication in the background, studies for increasing the capacity of the backbone network are being conducted energetically. In increasing the transmission capacity, a technique of increasing the symbol rate (modulation code creation speed) per wavelength and multiplexing on the wavelength axis by using wavelength division multiplexing (WDM) is used. Since the usable wavelength range is limited by the band of the erbium-doped optical amplifier, a technique for effectively utilizing the limited wavelength resources is required.

  Orthogonal frequency division multiplexing (OFDM) is a technique used to effectively utilize limited wavelength resources, and is a general-purpose technique in the field of radio.

  As a technique for OFDM-modulating an optical signal, there is a method of electrically generating an OFDM signal and driving an optical modulator as in the case of radio (see Patent Document 1 and Non-Patent Document 1). When this method is used, the optical system is simple. However, since the modulator and the modulator driving unit are required to have a band about N times the symbol rate, there is a problem that these bands become a limiting factor.

  On the other hand, all-optical OFDM has been proposed in which subcarrier light is modulated by an optical modulator and multiplexed (see Patent Documents 2 and 3). FIG. 13 shows a configuration of a conventional OFDM modulator. First, a plurality of subcarrier lights are generated by the multicarrier generation circuit 101, then the subcarrier lights are discriminated into subcarrier lights by the optical demultiplexing unit 102, and data modulation is performed by the optical orthogonal modulators 103a and 103b, respectively. Are combined by the combining unit 104 to obtain a modulated output. As disclosed in Patent Document 3, the optical demultiplexing unit 102 may be configured by delay interferometers 105, 106a, and 106b. In this way, a high extinction ratio can be obtained even when the optical frequency grid of WDM signals (the optical frequency interval between WDM optical signals) and the subcarrier interval differ to some extent. FIG. 1 shows a case where the number of subcarriers is two. In this case, the optical circuit on the transmission side is relatively simple, which is promising as a next-generation high-speed transmission technique.

JP 2005-311722 A JP 2009-017320 A JP 2009-198914 A

Sander L. Jansen, et al, “Coherent Optical 25.8-Gb / s OFDM Transmission Over 4160-km SSMF,” JOURNAL OF LIGHTWAVE TECHNOLOGY, 2008, VOL. 26, NO. 1, pp. 6-15

  However, in the configuration of this conventional all-optical OFDM modulator, it is necessary to use the delay interferometers 105, 106a, and 106b in the optical demultiplexing unit 102 for subcarrier discrimination, which increases the circuit size. there were. In order to set the WDM optical frequency grid to 100 GHz, it is necessary to set the free spectrum range (FSR: Free Spectrum Range) of the delay interferometer to about 50 GHz (see Patent Document 3). If this delay interferometer is made of a silica-based optical waveguide (N = 1.49 or so), the optical path length difference of the delay interferometer is about 4 mm. In order to set the frequency interval of the wavelength channel to the 50 GHz interval, which has recently been applied, the optical path length difference is about double 8 mm, and an optical branching unit with a large circuit size is required.

  In general, the lithium niobate waveguide or the quartz-based optical waveguide constituting the delay interferometer has a temperature dependency of the refractive index, so that there is a problem that the center wavelength of the delay interferometer changes depending on the environmental temperature. In order to solve this, it is necessary to adjust the temperature of the delay interferometer or make it temperature-independent. However, the temperature adjustment complicates the mounting of the modulator module and increases the power consumption (generally several W). There is a problem, and temperature independence has a problem of causing an increase in loss (generally ˜1 dB).

  Further, since the FSR of the delay interferometer needs to be set in accordance with the optical frequency grid and the subcarrier spacing, it is necessary to change the design of the delay interferometer for different optical frequency grids, There was a problem that it was necessary.

  The present invention has been made in view of the prior art as described above, and an object of the present invention is to provide a small optical modulator capable of simultaneously generating and modulating subcarriers and an optical modulation device using the same. There is.

In order to solve the above problems, the present invention provides an optical modulator, which is disposed between an input optical port, an output optical port, and the input optical port and the output optical port. An optical amplitude modulation unit and an optical phase modulation unit optically connected in cascade, and the optical amplitude modulation unit is driven by an electrical periodic modulation signal phase-modulated by a first electrical signal, and has two subcarriers And the optical phase modulation unit is driven by a second electrical signal that is paired with the first electrical signal, and the two subcarriers are phase-shifted . It characterized then modulating the phase of the phase.

  According to a second aspect of the present invention, in the optical modulator according to the first aspect, N sets (N: an integer of 2 or more) of the optical amplitude modulation unit and the optical phase modulation unit connected in cascade are used for the input. Between the optical port and the N sets of cascade-connected optical amplitude modulation units and optical phase modulation units, an optically connected 1-input N-output multicarrier generation unit and the N sets of cascade connection And an optical MUX with N inputs and one output optically connected between the optical amplitude modulator and optical phase modulator and the output optical port.

  According to a third aspect of the present invention, in the optical modulator according to the first or second aspect, the optical amplitude modulation unit is arranged in a stage preceding the optical phase modulation unit.

  According to a fourth aspect of the present invention, in the optical modulator according to any one of the first to third aspects, the optical amplitude modulation unit is a Mach-Zehnder interferometer.

  According to a fifth aspect of the present invention, in the optical modulator according to the fourth aspect, the modulation degree of the optical amplitude modulation section is between 1.5 rad and 2.5 rad.

  According to a sixth aspect of the present invention, in the optical modulator according to the fourth or fifth aspect, the multiplexing unit of the Mach-Zehnder interferometer of the optical amplitude modulation unit is a 2 × 2 optical coupler, and one output of the 2 × 2 optical coupler The port is optically connected to the monitor PD.

  According to a seventh aspect of the present invention, in the optical modulator according to any one of the fourth to sixth aspects, the Mach-Zehnder interferometer includes a low speed control electrode and a high speed control electrode.

  According to an eighth aspect of the present invention, in the optical modulator according to any one of the first to seventh aspects, the optical phase modulation section is a nested Mach-Zehnder interferometer.

  A ninth aspect of the present invention is an optical modulation device, wherein the optical modulator according to any one of the first to eighth aspects, an electric signal generating unit that generates an electric periodic signal, and the electric signal generating unit An electrical phase modulation unit that modulates the electrical periodic signal output from the first electrical signal and outputs the electrical periodic modulation signal to the optical amplitude modulation unit.

  The present invention has the effect of reducing the size by performing subcarrier generation and modulation simultaneously.

It is a figure showing the structure of the light modulation apparatus which concerns on 1st Embodiment of this invention. It is a figure showing a modulation degree and a normalized amplitude. It is a figure showing the relationship between an optical phase and an electrical phase. It is a figure which shows the coincidence of a transmission signal and a demodulated signal. It is a figure which shows the structural example of an electrical phase modulation | alteration part. It is a figure which shows the implementation example of the optical modulation apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the output light spectrum by the light modulation apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the light modulation apparatus which concerns on the 1st modification of 1st Embodiment of this invention. It is a figure which shows the light modulation apparatus which concerns on the 2nd modification of 1st Embodiment of this invention. It is a figure which shows the light modulation apparatus which concerns on the 3rd modification of 1st Embodiment of this invention. It is a figure which shows the light modulation apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the output light spectrum by the light modulation apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the structure of the conventional OFDM modulator.

  Hereinafter, embodiments of the present invention will be described in detail.

(First embodiment)
FIG. 1 shows a configuration of an optical modulation device according to the first embodiment of the present invention. In the optical modulation device of the first embodiment, the input optical port 11 is optically connected to the optical amplitude modulation unit 12, the optical amplitude modulation unit 12 is optically connected to the optical phase modulation unit 13, and optical phase modulation is performed. The unit 13 is optically connected to the output optical port 14. The electrical signal generator 15 is electrically connected to the electrical phase modulator 16, and the output of the electrical phase modulator 16 is electrically connected to the optical amplitude modulator 12.

  Portions corresponding to the optical modulator are an input optical port 11, an optical amplitude modulator 12, an optical phase modulator 13, and an output optical port 14.

  In the light input to the input optical port 11, two subcarriers are generated by the optical amplitude modulation unit 12, and the opposite phase of the phase is simultaneously modulated. These two subcarriers are then modulated in phase by the optical phase modulator 13 and output from the output optical port 14.

  Hereinafter, the details of the operation principle will be described using mathematical expressions.

An optical electric field E of an optical OFDM signal composed of two optical signals subjected to phase shift modulation (PSK) has a phase shift amount of the first optical signal as φ ₁ (t) and a phase shift amount of the second optical signal. Is φ ₂ (t), the optical angular frequency of the first optical signal is ω ₀ + Ω, and the optical angular frequency of the second optical signal is ω ₀ −Ω.

Formula 1 is transformed into the following formula.

Here, θ ₁ and θ ₂ are quantities defined by the following equations.

Equation 2 shows that the optical amplitude of an optical OFDM signal is an optical signal having an angular frequency Ω obtained by optical phase modulation (θ ₁ ) expressed in terms of exp and electrical phase modulation (θ ₂ ) expressed in terms of cos. It shows that it is realized by modulation.

  On the other hand, in the optical modulation device according to the first embodiment of the present invention shown in FIG. 1, the output of the electric signal generator 15 is Mcos (Ωt), and the output function for the electric input of the optical amplitude modulator 12 is a sine wave. Then

It becomes. Equation 4 can be further expanded by a Bessel function to obtain the following equation.

  Looking at the term of the fundamental wave (n = 0) in Formula 5, it can be seen that Formula 2 matches with the exception of the coefficient. Therefore, it can be seen that a 2-subcarrier OFDM PSK signal can be generated by the optical modulation apparatus configured as shown in FIG. In the optical modulation device having the configuration shown in FIG. 1, the optical circuit is greatly simplified as compared with the conventional optical modulator shown in FIG. 13, and thus a small and low-cost optical modulation device can be provided. .

  As apparent from Equation 5, the obtained modulation signal depends on the modulation degree M. FIG. 2 shows the relationship between the modulation degree M and the normalized output amplitude when the ideal OFDM modulator output amplitude is 1. From FIG. 2, it can be seen that in order to increase the fundamental wave (n = 0) in Equation 5, it is desirable to set M between 1.5 and 2.5.

FIG. 3 shows the phase shift amounts φ ₁ and φ ₂ of QPSK of each subcarrier based on Equation 3 when the 2-subcarrier OFDM-QPKS is generated by the optical modulation apparatus having the configuration shown in FIG. The relationship between the phase modulation amounts θ ₁ and θ ₂ for light and electricity is shown. The combinations of the phase shift amounts φ ₁ and φ ₂ , that is, the phase modulation amounts θ ₁ and θ ₂ are each 7-level modulation.

  FIG. 4 shows transmission data and demodulated data when a 2-carrier OFDM-QPSK optical signal is generated and demodulated by the optical modulation apparatus having the configuration shown in FIG. The modulation degree M is set to M = 1.88 from FIG. Since QPSK modulation is used, 2-bit data (DATA # 1-1, DATA # 1-2) for subcarrier # 1, and 2-bit data (DATA # 2-1, DATA # 2-2) for subcarrier # 2. )It is shown. FIG. 4 shows that the transmission signal and the demodulated signal are the same for all data.

  In FIG. 4, each subcarrier is modulated by QPSK for the sake of simplicity. However, the present invention is not limited to this example, and more than 3 bits 8PSK, 4 bits 16PSK, or more. It is also applicable to n-PSK.

  FIG. 5 shows a configuration of the electrical phase modulation unit 16 of the light modulation device according to the first embodiment of the present invention. The electrical phase modulation unit of FIG. 5 is electrically connected to two outputs of the input electrical port 21, the 90 ° phase shifter 22 electrically connected to the input electrical port 21, and the 90 ° phase shifter 22. It comprises a connected multiplier 23a, 23b, an adder 25 electrically connected to the output of the multiplier 23a, 23b, and an output electrical port 26 electrically connected to the adder 25. The multipliers 23a and 23b are provided with control signal input terminals 24a and 24b, respectively, and multiply the signal from the 90 ° phase shifter 22 and the control signal and output the result.

  If the electrical signal input to the input electrical port 21 is expressed as cosΩt, the following signal is obtained at the output electrical port 26 except for a non-essential coefficient.

数式６より分かるように、出力はφだけ位相シフトした電気信号となる。

As can be seen from Equation 6, the output is an electrical signal phase-shifted by φ.

  FIG. 6 is a diagram illustrating an implementation example of the optical modulator according to the first embodiment of the present invention. On the substrate 31, an optical amplitude modulation unit 12 and an optical phase modulation unit 13 are installed. The optical amplitude modulation section 12 is optically connected to two outputs of the 1 × 2 optical coupler 34, the low speed control electrodes 35a and 35b and the high speed control electrodes 36a and 36b provided at the output of the 1 × 2 optical coupler 34, and the 1 × 2 optical coupler 34, respectively. It consists of a 2 × 2 optical coupler 39 connected. The optical phase modulator 13 includes a high-speed control electrode 36 c optically connected to one output of the 2 × 2 optical coupler 24.

  The input side of the 1 × 2 optical coupler 34 is optically connected to the optical fiber 32a by the optical fiber block 33a for securing the connection strength to form the input optical port 11. Further, the output side of the 2x2 optical coupler 39 provided with the high-speed control electrode 36c is optically connected to the optical fiber 32b by the optical fiber block 33b for securing the connection strength to form the output optical port 14. ing.

  The low speed control electrodes 35a and 35b are electrically connected to the DC terminals 41a and 41b provided on the housing 44 by the electric wiring 37, respectively, and the DC terminals 41a and 41b of the low speed control electrodes 35a and 35b are connected. The other side is dropped to the ground. The high-speed control electrodes 36a, 36b, and 36c are electrically connected to RF terminals 42a, 42b, and 42c that are also provided on the housing 44 by the electric wiring 37. Terminating resistors 38a, 38b, and 38c are provided on the opposite side of the high-speed control electrodes 36a, 36b, and 36c to which the RF terminals 42a, 42b, and 42c are connected.

  Further, the port of the 2 × 2 optical coupler 39 that is not connected to the optical fiber 32 b is optically connected to the monitor PD 40, and electrical signals from the monitor PD 40 are taken out from DC terminals 41 c and 41 d provided on the housing 44. Can do.

  On the other hand, the electrical signal generated by the electrical signal generator 15 is phase-modulated by the electrical phase modulator 16, and drives the RF terminals 42a and 42b in opposite phases via the RF driver 43a. The optical phase signal drives the RF terminal 42c through the RF driver 43b.

  Here, in the first embodiment of the present invention, lithium niobate can be used as the material of the substrate 31 for manufacturing the light modulator having low loss, low chirp and high efficiency. However, the present invention is not limited to this, and the material of the substrate 31 may be a semiconductor such as InP, GaAs, GaN, or Si, or an organic material such as an electro-optic polymer.

  In the first embodiment of the present invention, the 1 × 2 optical coupler 34, the low speed control electrode 35, the high speed control electrode 36, and the 2 × 2 optical coupler 39 are all on one substrate 31. This is because an optical modulation device with fewer steps can be provided. However, the present invention is not limited to this, and the 1 × 2 optical coupler 34 and the 2 × 2 optical coupler 39 are on the silica-based PLC, and the low speed control electrodes 35a and 35b and the high speed control electrodes 36a, 36b, and 36c are on the lithium niobate. It is also possible to adopt a configuration in which this is realized by multichip connection.

  In the first embodiment of the present invention, the optical amplitude modulation unit 12 is configured by a Mach-Zehnder interferometer. However, the present invention is not limited to this example, and a configuration for directly adjusting the amplitude, such as an EA modulator. It can also be.

  Furthermore, in the first embodiment of the present invention, the high-speed control electrodes 36a and 36b of both arms of the Mach-Zehnder interferometer have a so-called push-pull configuration, but a part of lithium niobate is inverted in polarization. Of course, a single electrode may be used.

  In the first embodiment of the present invention, the Mach-Zehnder interferometer includes the low-speed control electrodes 35a and 35b for bias adjustment, and further includes the monitor PD 40 for performing this control. However, the present invention is not limited to this example, and bias adjustment may be performed by other means such as a thermo-optic heater, and there is no monitor PD, or an optical semiconductor modulator or the like has a low speed control voltage. This can be substituted by a current value monitor.

  In the first embodiment of the present invention, the terminating resistors 38a, 38b, and 38c are provided on the side opposite to the input side of the high-speed control electrodes 36a, 36b, and 36c. This is because a traveling wave electrode can be configured with this configuration, and high-efficiency modulation with a large interaction between an electric signal and an optical signal can be performed. However, the present invention is not limited to this example, and the termination resistor 38a is used by using a lumped constant type electrode, or by using a progressive drive type electrode in which multistage lumped constant type electrodes are sequentially driven by CMOS. , 38b, 38c may be omitted.

  In the first embodiment of the present invention, the electric signals driven by the RF drivers 43a and 43b are amplified. However, when a modulation element having a small half-wave voltage is used, these RF drivers 43a and 43b are unnecessary.

  FIG. 7A shows an optical signal spectrum generated by a conventional OFDM modulator, and FIG. 7B shows a 2-subcarrier OFDM-QPSK signal generated by the optical modulation apparatus according to the first embodiment of the present invention. The optical signal spectrum is shown. As shown in FIGS. 7A and 7B, the optical modulation apparatus according to the first embodiment of the present invention also provides a spectrum equivalent to the optical signal spectrum generated by the conventional OFDM modulator. I understand that.

(Second Embodiment)
FIG. 8 shows a configuration of an optical modulation device according to the second embodiment of the present invention. In the second embodiment, the order of the optical amplitude modulation unit 12 and the optical phase adjustment unit 13 is changed with respect to the first embodiment, and the optical amplitude modulation unit 12 is provided after the optical phase adjustment unit 13. It is the composition which is. When the optical amplitude modulator 12 is provided with the PD monitor 40 as shown in FIG. 6 of the first embodiment, the optical phase adjuster is arranged so that the bias adjustment is not affected by the optical phase modulator 13. 13 is preferably after the optical amplitude modulation section 12, but even with such a configuration, subcarrier generation and modulation can be performed simultaneously as in the first embodiment.

  Portions corresponding to the optical modulator are an input optical port 11, an optical amplitude modulator 12, an optical phase modulator 13, and an output optical port 14.

(Third embodiment)
FIG. 9 shows a configuration of an optical modulation device according to the third embodiment of the present invention. In the third embodiment, not the Mach-Zehnder interferometer but an EA modulation element is used as the optical amplitude modulation unit 12. Even with such a configuration, subcarrier generation and modulation can be performed simultaneously as in the first embodiment.

  Portions corresponding to the optical modulator are an input optical port 11, an optical amplitude modulator 12, an optical phase modulator 13, and an output optical port 14.

(Fourth embodiment)
FIG. 10 shows a configuration of an optical modulation apparatus according to the fourth embodiment of the present invention. The fourth embodiment is the same as the first embodiment except that a so-called nested Mach-Zehnder interferometer is used as the optical phase adjustment unit 13. The optical phase adjusting unit 13 includes two 1 × 2 optical couplers 51, two 1 × 2 optical couplers 52 a and 52 b optically connected to two outputs of the 1 × 2 optical coupler 51, and two 1 × 2 optical couplers 52 a and 52 b, respectively. The 2x1 optical couplers 53a and 53b optically connected to the output and the 2x1 optical coupler 54 optically connected to the outputs of the two 2x1 optical couplers 53a and 53b.

  Here, the bias is adjusted so that an optical phase difference of π / 2 or −π / 2 is added to any one of the two outputs of the two 1 × 2 optical couplers 52a and 52b in total. Yes. The bias is adjusted so that an optical phase difference of π / 2 or −π / 2 is added to any one of the outputs of the two 2 × 1 optical couplers 53a and 53b.

  Even with such a configuration, subcarrier generation and modulation can be performed simultaneously as in the first embodiment.

  Portions corresponding to the optical modulator are an input optical port 11, an optical amplitude modulator 12, an optical phase modulator 13, and an output optical port 14.

(Fifth embodiment)
FIG. 11 shows the configuration of the light modulation device according to the fifth embodiment of the present invention. In the fifth embodiment, the input optical port 11 is optically connected to the multicarrier generator 61, and the optical amplitude modulators 12a, 12b, 12c, and 12d are optically connected to the outputs of the multicarrier generator 61, respectively. It is connected to the. Optical phase adjusters 13a, 13b, 13c, and 13d are optically connected to the outputs of the optical amplitude modulators 12a, 12b, 12c, and 12d, and the outputs of the optical phase adjusters 13a, 13b, 13c, and 13d are The optical MUX 65 is optically connected. The output of the optical MUX 65 is optically connected to the output optical port 14. The electrical signal generator 15 is electrically connected to the electrical phase shifters 16a, 16b, 16c, and 16d, and the outputs of the electrical phase shifters 16a, 16b, 16c, and 16d are the optical amplitude modulators 12a, 12b, 12c, 12d is electrically connected.

  The multicarrier generation unit 61 includes an optical amplitude modulation unit 62, an optical DEMUX 64 provided at the output of the optical amplitude modulation unit 62, and an electrical signal generation unit 63. The output of the electrical signal generation unit 63 is an optical signal. The amplitude modulation unit 62 is electrically connected.

  Portions corresponding to the optical modulator are an input optical port 11, a multicarrier generator 61, an optical amplitude modulator 12, an optical phase modulator 13, an optical MUX 65, and an output optical port 14.

  With such a configuration, each of the four subcarriers generated by the multicarrier generator is subjected to 2-subcarrier-QPSK modulation, and as a result, a 16-subcarrier OFDM-QPSK optical signal can be obtained.

  When driving under the OFDM condition, the drive frequency of the electrical signal generator 63 is preferably 2Ω, and the drive frequency of the electrical signal generator 15 is preferably Ω.

  In addition, from the viewpoint of obtaining multicarriers with uniform amplitude, the modulation degree of the optical amplitude modulation unit 62 is desirably set to 2.5 to 3.5 rad when the number of subcarrier generation is four.

  Here, in the fifth embodiment, the number of subcarriers generated in the multicarrier generator 61 is four, but up to this number, subcarriers of equal amplitude can be generated by the Mach-Zehnder optical amplitude modulator 62. Because. However, the present invention is not limited to this example, and the number of subcarriers may be two, three, or a number larger than four, such as six. When the number is larger than 4, the amplitude can be adjusted by the optical DEMUX 64 unit.

  Furthermore, in the fifth embodiment, the multicarrier generation unit 61 is configured by the Mach-Zehnder type optical amplitude modulation unit 62. However, the present invention is not limited to this example. For example, the multicarrier generation unit 61 is an optical loop including an optical frequency shifter. The multicarrier generation unit 61 can also be configured.

  Further, it is desirable that the optical DEMUX 64 and the optical MUX 65 are constituted by an arrayed waveguide grating filter. This is because this configuration can provide an optical modulator with excellent integration. However, the present invention is not limited to this example, and the optical DEMUX 64 and the optical MUX 65 are configured by a transversal optical filter, a lattice optical filter, or a thin film optical filter. Alternatively, N can be configured with an Nx1 splitter and a 1xN splitter, where N is the number of subcarriers generated by the subcarrier generator.

  FIG. 12 (a) shows the output optical spectrum of the conventional OFDM modulator, and FIG. 12 (b) shows the output of the 8-subcarrier OFDM-QPSK signal generated by the optical modulation apparatus according to the fifth embodiment of the present invention. An optical spectrum is shown. As shown in FIGS. 12A and 12B, it can be seen that an OFDM optical signal equivalent to the conventional one can be obtained even with the small and simple configuration of the fifth embodiment of the present invention.

  As described above in detail, by using the optical modulation device of the present invention, it is possible to generate a phase shift modulation signal of a plurality of subcarriers with a small and simple configuration.

DESCRIPTION OF SYMBOLS 11 Input optical port 12 Optical amplitude modulation part 13 Optical phase modulation part 14 Output optical port 15 Electrical signal generation part 16 Electrical phase modulation part 21 Input electrical port 22 90 degree phase shifter 23 Multiplier 24 Control signal input terminal 25 Adder 31 Substrate 32 Optical fiber 33 Optical fiber block 34 1x2 optical coupler 35 Low speed control electrode 36 High speed control electrode 37 Electrical wiring 38 Termination resistor 39 2x2 optical coupler 40 Monitor PD
41 DC terminal 42 RF terminal 43 RF driver 44 Case 51 1x2 optical coupler 52 1x2 optical coupler 53 2x1 optical coupler 54 2x1 optical coupler 61 Multicarrier generation unit 62 Optical amplitude modulation unit 63 Electric signal generation unit 64 Optical DEMUX
65 Hikari MUX
DESCRIPTION OF SYMBOLS 101 Optical subcarrier generator 102 Optical branching part 103 Optical quadrature modulator 104 Optical multiplexing part 105,106 Delay interferometer

Claims (9)

An optical port for input;
An optical port for output;
An optical amplitude modulation unit and an optical phase modulation unit that are optically connected in cascade, disposed between the input optical port and the output optical port;
The optical amplitude modulation unit is driven by an electrical periodic modulation signal phase-modulated with a first electrical signal to generate two subcarriers , and modulates the opposite phase of the phase of the two subcarriers , optical modulator the optical phase modulating unit is characterized by then modulating a phase component of the first electrical signal and the second being driven by an electric signal the two subcarriers paired phase. N sets (N: an integer of 2 or more) of the optical amplitude modulation unit and the optical phase modulation unit connected in cascade,
A 1-input N-output multicarrier generator optically connected between the optical port for input and the N sets of cascaded optical amplitude modulators and optical phase modulators;
An optical input MUX of N inputs and one output optically connected between the N sets of optically connected optical amplitude modulators and optical phase modulators connected in cascade, and the output optical port;
The optical modulator according to claim 1, further comprising:   The optical modulator according to claim 1, wherein the optical amplitude modulation unit is arranged in a stage preceding the optical phase modulation unit.   4. The optical modulator according to claim 1, wherein the optical amplitude modulation unit is a Mach-Zehnder interferometer.   The optical modulator according to claim 4, wherein a modulation degree of the optical amplitude modulation unit is between 1.5 rad and 2.5 rad.   6. The combining unit of the Mach-Zehnder interferometer of the optical amplitude modulation unit is a 2 × 2 optical coupler, and one output port of the 2 × 2 optical coupler is optically connected to a monitor PD. An optical modulator according to 1.   The optical modulator according to any one of claims 4 to 6, wherein the Mach-Zehnder interferometer includes a low-speed control electrode and a high-speed control electrode.   8. The optical modulator according to claim 1, wherein the optical phase modulator is a nested Mach-Zehnder interferometer. An optical modulator according to any one of claims 1 to 8;
An electrical signal generator for generating electrical periodic signals;
An electrical phase modulator that modulates the electrical periodic signal output from the electrical signal generator with the first electrical signal and outputs the electrical periodic modulated signal to the optical amplitude modulator;
An optical modulation device comprising:

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