JP2018146613A - Optical modulator and optical modulation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small size optical modulator capable of achieving satisfactory optical amplification characteristics.SOLUTION: An optical modulator 1 includes: a branching part 10 that branches an input beam of light into at least two beams of light; modulation parts 11 to 13 for modulating the branched beams of light; and multiplexing parts 14 to 17 for multiplexing the modulated beams of light and outputs a multiplexed beams of light as a beam of transmission light. The multiplexing parts 14 to 17 include: and optical waveguides 15 and 16 doped with rare earth ion for amplifying a beam of light which has a predetermined frequency; and an introduction port 176 for introducing an excitation ray to the optical waveguides 15 and 16 for exciting the rare earth ion.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an optical modulator and an optical modulation method.

  In a high-speed optical transmission system such as 100 GbpS, a digital coherent optical transceiver having an optical waveguide substrate in which various optical elements are formed on a semiconductor substrate is used (see, for example, Patent Documents 1 and 2). An optical waveguide substrate in which various optical elements are formed on a semiconductor substrate is also referred to as a planar waveguide. The planar waveguide is a substrate on which optical elements such as an optical directional coupler, a polarization-beam splitter (PBS), and an optical 90-degree hybrid circuit are formed. By adopting a planar waveguide capable of forming a plurality of elements on a single substrate, a digital coherent optical transceiver including an optical modulator can be miniaturized.

JP 2010-54925 A JP-A-8-242030

In addition, the digital coherent optical transceiver uses the light output from the light source as transmission light, and a part of the light output from the light source is divided by a beam splitter or the like to be used as local light. Power consumption can be reduced. In order to prevent the optical output power of the transmitted light from being reduced by using a part of the transmitted light as local light, the transmitted light is modulated by the optical modulator and then erbium doped fiber amplifier. , EDFA) or the like. EDFA includes an erbium-doped optical fiber of erbium ions (Er ⁺³⁾ is a length of several m doped in the core, by exciting erbium ions (Er ⁺³⁾ by the excitation light, the 1.55μm band It is an amplifier that amplifies light. The transmission light output from the light source is modulated by the optical modulator, then combined with the excitation light and amplified by the EDFA, thereby realizing a desired optical amplification characteristic.

  However, since the erbium-doped optical fiber included in the EDFA generally has a length of several meters, the digital coherent optical transceiver that amplifies the transmission light by the EDFA is not easy to downsize.

  In one embodiment, an object is to provide an optical modulator that is small in size and can obtain good optical amplification characteristics.

  In one aspect, the optical modulator is modulated by the demultiplexing unit that demultiplexes the input light into at least two lights, the modulation unit that modulates the light demultiplexed by the demultiplexing unit, and the modulation unit A combining unit that combines the light and outputs the combined light as transmission light. The multiplexing unit includes an optical waveguide doped with rare earth ions that amplifies light having a predetermined frequency, and an introduction port that introduces excitation light that excites rare earth ions into the optical waveguide.

  In one embodiment, a small size and good optical amplification characteristics can be obtained.

(A) is a block diagram of a digital coherent optical transceiver including a reception front end as an example of a related optical modulator, and (b) is an internal block diagram of the EDFA shown in (a). It is an internal block diagram of the optical modulator shown to Fig.1 (a). 1 is a block diagram of a digital coherent optical transceiver including an optical modulator according to a first embodiment. FIG. FIG. 4 is an internal block diagram of the optical modulator shown in FIG. 3. (A) is a perspective view of an example of the first doped waveguide, (b) is a front view of the first doped waveguide shown in (a), and (c) is another example of the first doped waveguide. (D) is a front view of the first doped waveguide shown in (c). It is a figure for demonstrating operation | movement of the 1st dope waveguide shown in FIG. 4, a 2nd dope waveguide, and an optical directional coupler. It is an internal block diagram of the optical modulator which concerns on 2nd Embodiment. It is a figure for demonstrating operation | movement of the 1st dope waveguide shown in FIG. 7, a 2nd dope waveguide, and PBC. It is an internal block diagram of the optical modulator which concerns on 3rd Embodiment. (A) is a figure which shows the arrangement | positioning relationship between the 1st dope waveguide and 2nd dope waveguide shown in FIG. 10, and a radiation detection sensor, (b) is the 1st dope waveguide shown to (a), It is a schematic perspective view of a 2nd dope waveguide and a radiation detection sensor, (c) is sectional drawing containing the 1st dope waveguide shown in (a), a 2nd dope waveguide, and a radiation detection sensor. It is an internal block diagram of the optical modulator which concerns on a modification.

  Hereinafter, an optical modulator and an optical modulation method according to an embodiment will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments.

(Optical modulator related to the optical modulator according to the embodiment)
Before describing the optical modulator and the optical modulation method according to the embodiment, an optical modulator related to the optical modulator according to the embodiment will be described.

  FIG. 1A is a block diagram of a digital coherent optical transceiver including an associated optical modulator, and FIG. 1B is an internal block diagram of the EDFA shown in FIG.

  The digital coherent optical transceiver 900 includes a digital signal processor (DSP) 901, a digital / analog converter 902, and an analog / digital converter 903. The digital coherent optical transceiver 900 further includes a light source 911, a semiconductor optical amplifier (SOA) 912, a beam splitter 913, a modulation driver 914, an optical modulator 915, and an EDFA 916. The digital coherent optical transceiver 900 further includes a reception front end 917.

  The DSP 901 receives the digital transmission signals Tx1 to Tx_n, performs predetermined processing on the data corresponding to the input digital transmission signals Tx1 to Tx_n, and converts the digital transmission signal indicating the data subjected to the predetermined processing to digital analog Output to the converter 902. The DSP 901 receives a digital reception signal from the analog-digital converter 903, executes predetermined processing on data corresponding to the input digital reception signal, and a digital reception signal Rx1 indicating the data that has been subjected to the predetermined processing ~ Rx_n is output. The digital-analog converter 902 digital-analog converts the digital transmission signal input from the DSP 901 to generate an analog transmission signal, and outputs the generated analog transmission signal to the modulation driver 914. The analog-digital converter 903 performs analog-digital conversion on the analog reception signal input from the reception front end 917 to generate a digital transmission signal, and outputs the generated digital reception signal to the DSP 901.

  The light source 911 is, for example, a distributed feedback (DFB) laser, a SG-DBR (sampled grating-distributed bragg reflector) laser, a ring resonator laser, or the like, and outputs a coherent light having desired optical characteristics. It is. The coherent light output from the light source 911 is, for example, 1.55 μm band light.

  The SOA 912 is an amplifier that is formed of a semiconductor material such as GaAs / AlGaAs and amplifies coherent light input from the light source 911. The beam splitter 913 is, for example, a pair of prisms obtained by joining the inclined surfaces of each other, and divides the coherent light amplified by the SOA 912 into two lights at a predetermined ratio of 1: 1. The beam splitter 913 outputs one of the divided lights to the optical modulator 915 and outputs the other divided light to the reception front end 917. The modulation driver 914 outputs the analog transmission signal input from the digital-analog converter 902 to the optical modulator 915. The optical modulator 915 outputs modulated light obtained by modulating coherent light output from the light source 911 to the EDFA 916 based on the analog transmission signal input via the modulation driver 914. Since the structures and functions of the SOA 912, the beam splitter 913, and the modulation driver 914 are widely known, detailed description thereof is omitted here. The optical modulator 915 is formed of, for example, a planar lightwave circuit (PLC) and an LN element, and generates modulated light by performing coherent light quaternary phase-shift keying (QPSK).

  FIG. 2 is an internal block diagram of the optical modulator 915.

  The optical modulator 915 includes a beam splitter 930, a first QPSK circuit 931, a second QPSK circuit 932, a polarization rotator 933, and a polarization beam combiner (PBC) 934. The beam splitter 930 splits the light input from the beam splitter 913 on a one-to-one basis, and outputs the split light to each of the first QPSK circuit 931 and the second QPSK circuit 932. Each of the first QPSK circuit 931 and the second QPSK circuit 932 performs four-phase shift keying on the light input from the beam splitter 930. The first QPSK circuit 931 outputs the four-phase shift keyed light to the polarization rotator 933, and the second QPSK circuit 932 outputs the four-phase shift keyed light to the PBC 934. The polarization rotator 933 polarizes the light input from the first QPSK circuit 931 by 90 degrees and outputs the polarized light to the PBC 934. The PBC 934 combines the light input from each of the second QPSK circuit 932 and the polarization rotator 933 and outputs the combined light to the DFA 916. Since the structures and functions of the beam splitter 930, the first QPSK circuit 931, the second QPSK circuit 932, the polarization rotator 933, and the PBC 934 are widely known, detailed description thereof is omitted here.

The EDFA 916 includes a pumping light laser 921, a multiplexer 922, and an optical amplification fiber 923. The excitation light laser 921 is, for example, a distributed feedback laser, an SG-DBR laser, a ring resonator laser, or the like, and excitation light for exciting erbium ions (Er ⁺³ ) in the 0.98 μm band or 1.48 μm band. And the generated excitation light is output to the multiplexer 922. The multiplexer 922 is, for example, a WDM coupler, and combines the modulated light input from the optical modulator 915 and the excitation light input from the excitation light laser 921 and outputs the combined light to the optical amplification fiber 923. The optical amplifying fiber 923 is, for example, an optical fiber having a length of several meters in which erbium ions (Er ⁺³ ) are doped in the core, and when the pumping light is input from the pumping light laser 921, 1.55 μm. This amplifier amplifies the band light. The reception front end 917 is a planar waveguide in which a plurality of optical elements are formed. For example, the reception front end 917 demodulates reception light modulated by QPSK, and converts the demodulated optical signal into an electrical signal.

  The digital coherent optical transceiver 900 can be reduced in size and power consumption by dividing a part of the light output from the light source 911 by the beam splitter 913 and using it as local light. Further, the digital coherent optical transceiver 900 can prevent the optical output power of the transmission light from being lowered by the EDFA 916 amplifying the transmission light modulated by the optical modulator 915.

  However, since the optical amplification fiber 923 included in the EDFA 916 has a length of several meters, it is not easy to reduce the size of the digital coherent optical transceiver.

(Outline of Optical Modulator According to Embodiment)
The optical modulator according to the embodiment includes a demultiplexing unit that demultiplexes input light into at least two lights, a modulation unit that modulates light demultiplexed by the demultiplexing unit, and light modulated by the modulation unit And a multiplexing unit that outputs the combined light as transmission light. The multiplexing unit of the optical modulator according to the embodiment includes an optical waveguide doped with rare earth ions that amplifies light having a predetermined frequency, and an introduction port that introduces excitation light that excites rare earth ions into the optical waveguide. . By having such a configuration, the optical modulator according to the embodiment can share the optical amplification function together with the optical modulation function. Since the optical modulator according to the embodiment can share the optical modulation function and the optical amplification function, the digital coherent optical transceiver can omit the EDFA. The digital coherent optical transceiver can be reduced in size by omitting the large EDFA.

(Configuration and Function of Optical Modulator According to First Embodiment)
FIG. 3 is a block diagram of a digital coherent optical transceiver including the optical modulator 1 according to the first embodiment, and FIG. 4 is an internal block diagram of the optical modulator 1.

  The digital coherent optical transceiver 100 includes a DSP 101, a digital / analog converter 102, and an analog / digital converter 103. The digital coherent optical transceiver 100 further includes a light source 111, an SOA 112, a beam splitter 113, a modulation driver 114, an optical modulator 1, a reception front end 117, and a pump laser 118.

  The configuration and function of the DSP 101 to analog-digital converter 103 are the same as the configuration and function of the DSP 901 to analog-digital converter 903. The configurations and functions of the light source 111, the SOA 112, the modulation driver 114, and the reception front end 117 are the same as the configurations and functions of the light source 911, the SOA 912, the modulation driver 914, and the reception front end 917. Therefore, detailed descriptions of the configurations and functions of the DSP 101 to the analog-digital converter 103, the light source 111, the SOA 112, the modulation driver 114, and the reception front end 117 are omitted here.

  The beam splitter 113 is, for example, a pair of prisms obtained by joining the inclined surfaces to each other, and divides the coherent light amplified by the SOA 112 into two lights at a predetermined ratio at a ratio of 100: 1. The beam splitter 913 outputs the light having the ratio of 1 to the optical modulator 115 and the light having the ratio of 100 to the reception front end 117.

The excitation laser 118 is, for example, a distributed feedback laser, an SG-DBR laser, a ring resonator laser, or the like. The excitation laser 118 generates excitation light for exciting erbium ions (Er ⁺³ ) in the 0.98 μm band or 1.48 μm band, and outputs the generated excitation light to the optical modulator 1. For example, the P wave component and the S wave component of the excitation light generated by the excitation laser 118 are set to 50%. In one example, the excitation light is introduced into a fiber twisted by 45 degrees, so that each of the P wave component and the S wave component is set to 50%. In another example, the excitation light is introduced into the half-wave plate so that each of the P wave component and the S wave component is set to 50%. Since the excitation laser 118 generates heat, it is preferably disposed outside the optical modulator 1.

  The optical modulator 1 includes a beam splitter 10, a first QPSK circuit 11, a second QPSK circuit 12, a polarization rotator 13, a PBC 14, a first doped waveguide 15, a second doped waveguide 16, and an optical modulator. And a directional coupler 17. The beam splitter 10 is a demultiplexing unit that demultiplexes input light into at least two lights, and the first QPSK circuit 11, the second QPSK circuit 12, and the polarization rotator 13 are light demultiplexed by the demultiplexing unit. Is a modulation unit that modulates. The PBC 14, the first doped waveguide 15, the second doped waveguide 16, and the optical directional coupler 17 multiplex the light modulated by the modulation unit, and output the combined light as transmission light It is.

  The beam splitter 1 splits the light input from the beam splitter 14 on a one-to-one basis, and outputs the split light to each of the first QPSK circuit 11 and the second QPSK circuit 12. Each of the first QPSK circuit 11 and the second QPSK circuit 12 performs four-phase shift keying on the light input from the beam splitter 10. The first QPSK circuit 11 outputs the four-phase shift keyed light to the polarization rotator 13, and the second QPSK circuit 932 outputs the four-phase shift keyed light to the PBC 14 via the first doped waveguide 15.

  The polarization rotator 13 polarizes the light input from the first QPSK circuit 11 by 90 degrees and outputs the polarized light to the PBC 14 via the first doped waveguide 15. The PBC 14 combines the light input from each of the second QPSK circuit 12 and the polarization rotator 13 and outputs the combined light to the DFA 916.

  Since the structures and functions of the beam splitter 10, the first QPSK circuit 11, the second QPSK circuit 12, the polarization rotator 13, and the PBC 14 are widely known, detailed description thereof is omitted here.

  FIG. 5A is a perspective view of an example of the first doped waveguide 15, and FIG. 5B is a front view of the first doped waveguide 15 shown in FIG. FIG. 5C is a perspective view of another example of the first doped waveguide 15, and FIG. 5D is a front view of the first doped waveguide 15 shown in FIG. 5C.

The first doped waveguide 15 is a waveguide type EDFA doped with erbium ions (Er ⁺³ ), and is also referred to as EDWA. The first doped waveguide 15 may be a ridge type as shown in FIGS. 5 (a) and 5 (b), or may be a buried type as shown in FIGS. 5 (c) and 5 (d). Good. The relative refractive index difference of the first doped waveguide 15 is about 0.5% to 1% when the optical modulator 1 is a quartz substrate, and 35 when the optical modulator 1 is a silicon photonics substrate. %.

When the first doped waveguide 15 is a ridge type, the size can be increased and the design is simplified. On the other hand, when the first doped waveguide 15 is a buried type, the size is reduced. The mode field diameter of the first doped waveguide 15 is, for example, 5 μm. Since the mode field diameter of the conventional waveguide is about 10 μm, the mode field diameter of the first doped waveguide 15 is approximately half the mode field diameter of the conventional waveguide. Since the first doped waveguide 15 guides not only received light but also pumping light having a shorter wavelength than the received light, the mode field diameter may be about half that of the conventional one. Erbium ions (Er ⁺³ ) may be doped into the first doped waveguide 15 during crystal growth, or may be doped into the first doped waveguide 15 after crystal growth.

  Since the second doped waveguide 16 has the same structure as the first doped waveguide 15, the description of the structure of the second doped waveguide 16 is omitted here.

  FIG. 6 is a diagram for explaining operations of the first doped waveguide 15, the second doped waveguide 16, and the optical directional coupler 17.

  The optical directional coupler 17 includes a first waveguide 171, a second waveguide 172, a first port 173, a second port 174, a third port 175, and a fourth port 176. The first port 173 is disposed at one end of the first waveguide 171, the second port 174 is disposed at one end of the second waveguide 172, the third port 175 is disposed at the other end of the first waveguide 171, The 4-port 176 is disposed at the other end of the second waveguide 172.

  The first port 173 is connected to the PBC 14, the third port 175 is output with transmission light, and the fourth port 176 is input with excitation light generated by the excitation laser 118. The excitation light input from the fourth port 176 is introduced by 50% into each of the first doped waveguide 15 and the second doped waveguide 16 via the first port 173 and the PCB 14. The first doped waveguide 15 and the second doped waveguide 16 function as amplifiers that amplify the lights P1 and P2 output from the first QPSK circuit 11 and the second QPSK circuit 12 when the excitation light is introduced.

  The light P1 output from the first QPSK circuit 11 is amplified in the first doped waveguide 15. The light P1 output from the second QPSK circuit 12 is amplified in the second doped waveguide 16.

(Operational effect of the optical modulator according to the first embodiment)
Since the optical modulator 1 uses the light amplified in the first doped waveguide 15 and the second doped waveguide 16 as transmission light, the digital coherent optical transceiver 100 uses the transmission light output from the optical modulator 915. The EDFA to be amplified can be omitted. The digital coherent optical transceiver 100 can be miniaturized because the EDFA can be omitted.

(Configuration and function of optical modulator according to second embodiment)
FIG. 7 is an internal block diagram of the optical modulator 2 according to the second embodiment.

  The optical modulator 2 is different from the optical modulator 1 in that it does not have the optical directional coupler 17. Further, the optical modulator 2 is different from the optical modulator 1 in that the excitation light generated by the excitation laser 118 is input to the PBC 14. Since the configurations and functions of the components of the optical modulator 2 other than the PBC 14 are the same as the configurations and functions of the components of the optical modulator 1 with the same reference numerals, detailed description thereof is omitted here.

  FIG. 8 is a diagram for explaining the operation of the first doped waveguide 15, the second doped waveguide 16, and the PBC 14.

  The PBC 14 includes a first waveguide 141, a second waveguide 142, a first port 143, a second port 144, a third port 145, and a fourth port 146. The first port 143 is disposed at one end of the first waveguide 141, the second port 144 is disposed at one end of the second waveguide 142, the third port 145 is disposed at the other end of the first waveguide 141, The 4-port 146 is disposed at the other end of the second waveguide 142.

  The first port 143 is connected to the first doped waveguide 15, and the second port 144 is connected to the second doped waveguide 16. Transmission light is output to the third port 145, and excitation light generated by the excitation laser 118 is input to the fourth port 146. The excitation light input from the fourth port 146 is introduced 50% into each of the first doped waveguide 15 and the second doped waveguide 16 through the first port 173. The first doped waveguide 15 and the second doped waveguide 16 function as amplifiers that amplify the lights P1 and P2 output from the first QPSK circuit 11 and the second QPSK circuit 12 when the excitation light is introduced.

(Operational effect of the optical modulator according to the second embodiment)
The optical modulator 2 introduces the pump light into the pump light via the fourth port 146 which is a surplus port of the PBC 14 without adding a new element, and uses the first doped waveguide 15 and the second doped waveguide 16 as an amplifier. Can function.

(Configuration and Function of Optical Modulator According to Third Embodiment)
FIG. 9 is an internal block diagram of the optical modulator 3 according to the third embodiment.

  The optical modulator 3 is different from the optical modulator 2 in that it includes a radiation light detection sensor 18. Since the configuration and functions of the components of the optical modulator 3 other than the radiated light detection sensor 18 are the same as the configurations and functions of the components of the optical modulator 2 with the same reference numerals, detailed description thereof is omitted here.

  FIG. 10A is a diagram showing the positional relationship between the first doped waveguide 15 and the second doped waveguide 16 and the radiation detection sensor 18. FIG. 10B is a schematic perspective view of the first doped waveguide 15, the second doped waveguide 16 and the radiation detection sensor 18, and FIG. 10C is the first doped waveguide 15 and the second doped waveguide. 16 and a cross-sectional view including the radiation detection sensor 18.

  The synchrotron radiation detection sensor 18 is, for example, a photodiode, and is disposed so as to cover both the first doped waveguide 15 and the second doped waveguide 16, and the first doped waveguide 15 and the second doped waveguide 16 are separated from each other. The emitted radiation is detected.

  The emitted light detection sensor 18 outputs the detected intensity of the emitted light to a gain control unit (not shown), and the gain control unit controls the excitation laser 118 according to the intensity of the emitted light input from the emitted light detection sensor 18. .

(Operational effects of the optical modulator according to the third embodiment)
Since the optical modulator 3 includes the radiation detection sensor 18 that detects the radiation emitted from the first doped waveguide 15 and the second doped waveguide 16, a part of the transmission light is divided by a beam splitter or the like. It is not necessary to measure the intensity of the transmitted light. Since the optical modulator 3 can measure the intensity of the transmission light without dividing a part of the transmission light, there is no possibility that the transmission light is lowered due to the intensity measurement.

(Comparison of optical modulator according to the embodiment and other technologies)
Table 1 shows a comparison between the optical modulator according to the embodiment and other technologies. In Table 1, EDFA indicates characteristics when light is amplified by EDFA, SOA indicates characteristics when light is amplified by SOA, and EDWA indicates characteristics of the optical modulator according to the embodiment.

  When light is amplified by EDFA, optical gain, NF characteristics, efficiency and flexibility are very good. However, since the EDFA has an optical fiber having a length of several meters, there is a problem that the size is increased. When the light is amplified by the SOA, the optical gain is very good and the size can be reduced. However, since the waveform deteriorates due to the pattern effect, the SOA can be used to amplify the optical signal modulated by the modulator. There is a problem that it is not preferable.

Since the optical modulator according to the embodiment that amplifies light by EDWA is a digital coherent optical receiver that amplifies only one frequency band, the optical gain characteristic is improved. Further, since the optical modulator according to the embodiment is optical amplification on the transmission side, the optical SN is high and the influence of noise light can be ignored. In addition, the optical modulators according to the second and third embodiments do not require a multiplexer such as a WDM coupler by using a surplus port of a certain directional coupling unit in advance. In addition, since the optical receiver according to the embodiment has a structure in which a plurality of optical paths are amplified with a single excitation light source without actual insertion loss, excitation efficiency is improved. Moreover, since the optical receiver according to the embodiment performs backward pumping, the pumping efficiency is further improved. The optical modulator according to the embodiment is flexible because a waveguide type EDFA doped with erbium ions (Er ⁺³ ) is integrated with a modulator manufactured with a waveguide for a digital transmission / reception device. Is expensive.

(Modification of Optical Modulator According to Embodiment)
In the optical modulators 1 to 3, a waveguide type EDFA doped with erbium ions (Er ⁺³ ) is used. However, in the optical modulator according to the embodiment, other rare earth ^elements such as praseodymium ions (Pr ⁺³ ) are used. A waveguide type EDFA doped with ions may be used.

  In the optical modulators 1 to 3, the modulation unit includes two modulation circuits, the first QPSK circuit 11 and the second QPSK circuit 12, but in the optical modulator according to the embodiment, the number of modulation circuits included in the modulation unit. May be two or more.

  FIG. 11 is an internal block diagram of the optical modulator 4 according to the modification.

  The optical modulator 4 is formed by a first planar optical circuit 41, a second planar optical circuit 42, and an LN element 43, and includes a first coupler 51 to a fifth coupler 55, and a first modulation circuit 61 to a fourth modulation circuit. And a multi-value variable modulator having 64. The first coupler 51 to the third coupler 53 are 3 dB couplers, the fourth coupler 54 to the fifth coupler 55 are variable couplers, and the first modulation circuit 61 to the fourth modulation circuit 64 are Mach-Zehnder type modulators.

In the optical modulator 4, the waveguide type EDFA doped with erbium ions (Er ⁺³ ) is disposed between the fifth coupler 55, the second coupler 52, and the third modulation circuit 63 to the fourth modulation circuit 64. The In the optical modulator 4, by introducing pump light from the surplus port of the fifth coupler 55, the waveguide type EDFA doped with erbium ions (Er ⁺³ ) functions as an amplifier.

1-4 Optical modulator 10 Beam splitter 11 First QPSK circuit 12 Second QPSK circuit 13 Polarization rotator 14 PBC
DESCRIPTION OF SYMBOLS 15 1st dope waveguide 16 2nd dope waveguide 17 Optical directional coupler 18 Synchrotron radiation detection sensor

Claims (5)

A demultiplexing unit that demultiplexes input light into at least two lights;
A modulation unit for modulating the light demultiplexed by the demultiplexing unit;
Combining light modulated by the modulation unit, and outputting the combined light as transmission light,
The multiplexing unit is
An optical waveguide doped with rare earth ions for amplifying light having a predetermined frequency;
An introduction port for introducing excitation light for exciting the rare earth ions into the optical waveguide;
An optical modulator. The multiplexing unit further includes a multiplexing element that combines a plurality of lights input to the input port to generate transmission light,
The optical modulator according to claim 1, wherein the optical waveguide includes a plurality of optical waveguides connected to ports of the multiplexing element.   The optical modulator according to claim 2, wherein the introduction port is a port of the multiplexing element.   The optical modulator according to claim 1, further comprising a radiation detection sensor that detects radiation emitted from the optical waveguide. Demultiplexes the incoming light into at least two lights,
Modulate the demultiplexed light,
An optical waveguide doped with rare earth ions that amplifies light having a predetermined frequency by introducing pumping light for exciting the rare earth ions into an optical waveguide doped with rare earth ions that amplifies light having a predetermined frequency. Pass through the waveguide,
Outputting light that has passed through the optical waveguide as transmission light;
A light modulation method.

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