Optical transmission device and optical communication system

Abstract

Provided is an optical transmission device comprising: a light source unit that generates output light of a predetermined wavelength; an integrating unit that integrates an input signal; and a phase modulation unit that uses the integrated input signal to perform phase modulation on the output light to generate an optical frequency modulated signal, the phase modulation unit outputting the generated optical frequency modulated signal onto a transmission path. Provided is a light reception device comprising: an optical filter that performs slope detection processing on an optical frequency modulated signal transmitted through a transmission path, on the basis of the slope of attenuation characteristics, to thereby generate an optical intensity modulated signal; and a photoelectric conversion unit that converts the optical intensity modulated signal into an electric signal.

Description

Technical Field

[0001] The present invention relates to an optical transmission device reference and an optical communication system.

Background Art

[0002] An optical communication system that collectively converts a frequency division multiplexing (FDM) signal into a frequency modulation (FM) signal has been introduced into a video signal distribution system (see Non-Patent Documents 1 and 2).

[0003] FIG. 9 is a diagram showing a configuration example of an optical communication system (optical video distribution system). In an optical transmission device, a collective conversion unit 110 collectively converts a frequency division multiplexing signal into a broadband FM signal. The center frequency of this broadband FM signal is, for example, 3 GHz.

[0004] An optical intensity modulation unit 111 converts the FM signal into an optical intensity modulation signal. In the transmission line, an optical amplifier (for example, an erbium-doped fiber amplifier (EDFA)) and an optical distributor may be connected in multiple stages. Thereby, broadband optical transmission is possible.

[0005] In an optical reception device, a photoelectric conversion unit 112 converts the optical intensity modulation signal transmitted through the transmission line into a broadband FM signal. A delay detection unit 113 generates a demodulated signal by performing demodulation processing on the FM signal. An amplification unit 114 amplifies the level of the demodulated signal to a predetermined level.

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

[0007] The phase modulation unit 115 performs phase modulation on the output light of the first light source unit 117 using the frequency division multiplexed signal (input signal) input from the summing unit 116. The multiplexing unit 118 combines the phase-modulated output light with the output light of the second light source unit 119. The optical receiving unit 120 performs optical heterodyne reception on the combined output light. This yields a broadband FM signal centered on a frequency equal to the difference between the frequency of the first light source unit 117 and the frequency of the second light source unit 119. The optical intensity modulation unit 111 performs intensity modulation on the FM signal using the output light of the third light source unit 121.

[0008] In this way, the input signal is converted in one go to a wideband FM signal, making the optical communication system resistant to noise in the transmission path. However, there is a problem in that the configuration of the optical communication system using the FM all-in-one conversion method becomes complex.

[0009] In view of the above circumstances, the present invention aims to provide an optical transmitting device, an optical receiving device, and an optical communication system that can perform communication using FM batch conversion even with a simple configuration. [Means for solving the problem]

[0010] One aspect of the present invention is an optical transmission device comprising: a light source unit that generates output light of a predetermined wavelength; an integration unit that integrates an input signal; and a phase modulation unit that generates an optical frequency modulated signal by performing phase modulation on the output light using the integrated input signal, and outputs the generated optical frequency modulated signal to a transmission line.

[0011] One aspect of the present invention is an optical receiving device comprising an optical filter that generates an optical intensity modulated signal by performing slope detection processing on an optical frequency modulated signal transmitted through a transmission line based on the slope of the attenuation characteristics, and a photoelectric conversion unit that converts the optical intensity modulated signal into an electrical signal.

[0012] One aspect of the present invention is an optical communication system comprising an optical transmitting device and an optical receiving device, wherein the optical transmitting device comprises a light source unit that generates output light of a predetermined wavelength, an integration unit that integrates an input signal, and a phase modulation unit that generates an optical frequency modulated signal by performing phase modulation on the output light using the integrated input signal and outputs the generated optical frequency modulated signal to a transmission line, and the optical receiving device comprises an optical filter that generates an optical intensity modulated signal by performing slope detection processing on the optical frequency modulated signal transmitted through the transmission line based on the slope of the attenuation characteristics, and a photoelectric conversion unit that converts the optical intensity modulated signal into an electrical signal, wherein the optical communication system comprises an optical transmitting device and an optical receiving device. [Effects of the Invention]

[0013] This invention makes it possible to perform communication using FM batch conversion even with a simple configuration. [Brief explanation of the drawing]

[0014] [Figure 1] This figure shows an example of the configuration of an optical communication system in the first embodiment. [Figure 2] This is a flowchart showing an example of the operation of the optical communication system in the first embodiment. [Figure 3] This figure shows an example of the configuration of an optical communication system in the second embodiment. [Figure 4] It is a flowchart showing an operation example of an optical communication system in the second embodiment. [Figure 5] It is a diagram showing a configuration example of an optical communication system in the third embodiment. [Figure 6] It is a flowchart showing an operation example of an optical communication system in the third embodiment. [Figure 7] It is a diagram showing a configuration example of an optical communication system in a modified example. [Figure 8] It is a diagram showing a hardware configuration example of an optical communication system in each embodiment. [Figure 9] It is a diagram showing a configuration example of an optical communication system.

Modes for Carrying Out the Invention

[0015] Embodiments of the present invention will be described in detail with reference to the drawings. (First Embodiment) FIG. 1 is a diagram showing a configuration example of an optical communication system 1a in an embodiment. The optical communication system 1a (optical analog transmission system) is a system that communicates using optical signals. These optical signals are generated based on a batch conversion (FM batch conversion) into FM signals.

[0016] The optical communication system 1a includes an optical transmitter 2a and an optical receiver 3a. The optical transmitter 2a includes an adder 21, a light source unit 22, and a batch conversion unit 23. The batch conversion unit 23 includes an integrator 221 and a phase modulation unit 222. The optical receiver 3a includes an optical filter 31a and a photoelectric conversion unit 32. The optical communication system 1a may include a transmission line 4. The transmission line 4 includes an optical fiber. In the transmission line 4, optical amplifiers and optical distributors may be connected in multiple stages.

[0017] The adder 21 adds the first frequency division multiplexed signal and the second frequency division multiplexed signal. The first frequency division multiplexed signal is, for example, a multi-channel video signal including a cable TV signal (band: 90 to 770 MHz). The second frequency division multiplexed signal is, for example, a multi-channel video signal including an intermediate frequency signal of the right-hand circular polarization of a broadcast satellite and a communication satellite (BS / CS right-hand IF signal) (band: 1.0 to 2.1 GHz) and an intermediate frequency signal of the left-hand circular polarization of a broadcast satellite and a communication satellite (BS / CS left-hand IF signal) (2.2 to 3.2 GHz). The adder 21 outputs the addition result (input signal) of the first frequency division multiplexed signal and the second frequency division multiplexed signal to the integrator 221.

[0018] The light source unit 22 is a laser oscillator of a predetermined frequency, for example, a narrow linewidth laser diode. The light source unit 22 generates output light of a predetermined frequency (wavelength). The light source unit 22 outputs the output light of a predetermined frequency (wavelength) to the phase modulation unit 222. The integrator 221 (integration circuit) integrates the input signal. The phase modulation unit 222 generates an optical frequency modulation signal (optical FM signal) by performing phase modulation on the output light of the light source unit 22 using the integrated input signal. The transmission line 4 transmits the optical frequency modulation signal.

[0019] Based on the slope of the attenuation characteristic of the optical filter, the optical filter 31a converts the transmitted optical frequency modulation signal into an optical intensity modulation signal by performing slope detection processing on the transmitted optical frequency modulation signal. The photoelectric conversion unit 32 generates an input signal by converting the optical intensity modulation signal into an electrical signal. The photoelectric conversion unit 32 outputs the input signal to a predetermined external device (not shown).

[0020] Next, an operation example of the optical communication system 1a will be described. FIG. 2 is a flowchart showing an operation example of the optical communication system 1a in the first embodiment. The integrator 221 integrates the input signal (step S101). The phase modulation unit 222 performs phase modulation on the output light of the light source unit 22 using the integrated input signal (step S102).

[0021] The optical filter 31a performs slope detection on the transmitted optical frequency modulated signal based on the slope of the attenuation characteristics of the optical filter (step S103). The photoelectric conversion unit 32 converts the optical intensity modulated signal into an electrical signal (step S104).

[0022] As described above, the light source unit 22 generates output light of a predetermined wavelength. The integration unit 221 integrates the input signal. The phase modulation unit 222 generates an optical frequency modulated signal by performing phase modulation on the output light using the integrated input signal. The phase modulation unit 222 outputs the generated optical frequency modulated signal to the transmission line. The optical filter 31a generates an optical intensity modulated signal by performing slope detection processing on the optical frequency modulated signal transmitted through the transmission line 4 based on the slope of the attenuation characteristics. The photoelectric conversion unit 32 converts the optical intensity modulated signal into an electrical signal.

[0023] Thus, the optical transmitting device is reduced to include two light sources, one optical receiver (photodiode), and one optical intensity modulation unit. This makes it possible to perform communication using FM batch conversion even with a simple configuration. Furthermore, it is possible to transmit and receive optical signals at low cost. Even with a simple configuration, the optical communication system can be resistant to noise in the transmission path.

[0024] (Second Embodiment) In the second embodiment, the main difference from the first embodiment is that the optical receiving device includes a detection unit. The second embodiment will be explained focusing on the differences from the first embodiment.

[0025] Figure 3 shows an example configuration of the optical communication system 1b in the second embodiment. The optical communication system 1b comprises an optical transmitter 2b and an optical receiver 3b. The optical communication system 1b may also include a transmission line 4. The optical transmitter 2b comprises an adder 21, a light source 22, and a batch conversion unit 23. The batch conversion unit 23 comprises an integration unit 221 and a phase modulation unit 222. The optical receiver 3b comprises an optical filter 31b, a photoelectric conversion unit 32, a distribution unit 33, and a detection unit 34.

[0026] The optical filter 31b (tunable optical filter) is a tunable optical filter. The optical filter 31b transmits the optical frequency modulated signal at a wavelength specified by the detection unit 34 from among the wavelengths of the transmitted optical frequency modulated signal. The photoelectric conversion unit 32 converts the light transmitted through the optical filter 31b into an electrical signal. The distribution unit 33 outputs an electrical signal based on the transmitted optical frequency modulated signal to a predetermined external device (not shown) and to the detection unit 34.

[0027] The detection unit 34 continuously detects the intensity of the electrical signal based on the transmitted optical frequency modulated signal. The detection unit 34 specifies the wavelength of the optical frequency modulated signal that passes through the optical filter 31b so that the intensity of the electrical signal increases. For example, the detection unit 34 dynamically adjusts the wavelength of the optical frequency modulated signal that passes through the optical filter 31b to match the wavelength of the output light from the light source unit 22.

[0028] Next, we will explain an example of the operation of optical communication system 1b. Figure 4 is a flowchart showing an example of the operation of the optical communication system 1b in the second embodiment. The integration unit 221 integrates the input signal (step S201). The phase modulation unit 222 uses the integrated input signal to perform phase modulation on the output light of the light source unit 22 (step S202).

[0029] The optical filter 31b performs slope detection on the transmitted optical frequency modulated signal based on the slope of the attenuation characteristics of the optical filter (step S203). The photoelectric conversion unit 32 converts the optical intensity modulated signal into an electrical signal (step S204).

[0030] The distribution unit 33 outputs an electrical signal to a predetermined external device (not shown) and the detection unit 34 (step S205). The detection unit 34 continuously detects the intensity of the electrical signal based on the transmitted optical frequency modulation signal (step S206). The detection unit 34 specifies the wavelength of the optical frequency modulation signal to be transmitted through the optical filter 31b so that the intensity of the electrical signal increases (step S207).

[0031] As described above, the detection unit 34 detects the intensity of the electrical signal based on the transmitted optical frequency modulation signal. The optical filter 31b transmits the optical frequency modulation signal at a wavelength adjusted to increase the intensity of the electrical signal among the wavelengths of the transmitted optical frequency modulation signal. This makes it possible to perform communication using FM batch conversion even with a simple configuration. In addition, the optical communication system 1b can be resistant to noise in the transmission path 4.

[0032] (Third embodiment) In the third embodiment, the main difference from the first and second embodiments is that the optical communication system includes a control device. The third embodiment will be described primarily in terms of the differences from the first and second embodiments.

[0033] Figure 5 shows an example configuration of the optical communication system 1c in the third embodiment. The optical communication system 1c comprises an optical transmitter 2c, an optical receiver 3c, and a control device 5. The optical communication system 1c may also include a transmission line 4. The optical transmitter 2c comprises an adder 21, a light source unit 22, and a batch conversion unit 23. The batch conversion unit 23 comprises an integration unit 221 and a phase modulation unit 222. The optical receiver 3b comprises an optical filter 31a, a photoelectric conversion unit 32, a distribution unit 33, and a detection unit 34. The control device 5 (control unit) may be provided in the optical transmitter 2c. The control device 5 may be provided in the optical receiver 3c.

[0034] The detection unit 34 continuously detects the intensity of the electrical signal based on the transmitted optical frequency modulation signal. The detection unit 34 outputs the detection result of the electrical signal intensity to the control device 5. The control device 5 (monitoring network) specifies the wavelength (oscillation wavelength) of the output light of the light source unit 22 so that the intensity of the electrical signal increases. For example, the control device 5 dynamically adjusts the wavelength of the output light of the light source unit 22 to match the wavelength of the optical frequency modulation signal transmitted through the optical filter 31b.

[0035] Next, we will explain an example of the operation of optical communication system 1c. Figure 6 is a flowchart showing an example of the operation of the optical communication system 1c in the third embodiment. The integration unit 221 integrates the input signal (step S301). The phase modulation unit 222 uses the integrated input signal to perform phase modulation on the output light of the light source unit 22 (step S302).

[0036] The optical filter 31b performs slope detection on the transmitted optical frequency modulated signal based on the slope of the attenuation characteristics of the optical filter (step S303). The photoelectric conversion unit 32 converts the optical intensity modulated signal into an electrical signal (step S304).

[0037] The distribution unit 33 outputs an electrical signal to a predetermined external device (not shown) and the detection unit 34 (step S305). The detection unit 34 continuously detects the intensity of the electrical signal based on the transmitted optical frequency modulation signal (step S306). The detection unit 34 specifies the wavelength (frequency) of the output light from the light source unit 22 so that the intensity of the electrical signal increases (step S307).

[0038] As described above, the light source unit 22 generates output light of a predetermined wavelength adjusted to increase the intensity of the electrical signal based on the transmitted optical frequency modulation signal. This makes it possible to perform communication using FM batch conversion even with a simple configuration. In addition, the optical communication system 1c can be resistant to noise in the transmission path 4.

[0039] (modified version) Figure 7 shows an example configuration of optical communication system 1d in a modified example. Optical communication system 1d comprises a plurality of optical communication devices 100. In Figure 7, optical communication device 100-1 comprises an optical transmitter 2d-1 and an optical receiver 3d-1. Optical communication device 100-2 comprises an optical transmitter 2d-2 and an optical receiver 3d-2. Optical communication devices 100-1 and 100-2 face each other. Optical communication device 100-1 communicates with optical transmitter 2d-2 and optical receiver 3d-2 of optical communication device 100-2 using optical transmitter 2d-1 and optical receiver 3d-1.

[0040] As described above, the optical communication system 1d may have bidirectional capabilities.

[0041] (Example hardware configuration) Figure 8 shows examples of the hardware configuration of the optical communication device 101 in each embodiment. The hardware configuration of the optical communication device 101 corresponds to the hardware configuration of the optical transmitter 2a in the first embodiment, the hardware configuration of the optical receiver 3a in the first embodiment, the hardware configuration of the optical transmitter 2b in the second embodiment, the hardware configuration of the optical receiver 3b in the second embodiment, the hardware configuration of the optical transmitter 2c in the third embodiment, the hardware configuration of the optical receiver 3c in the third embodiment, the hardware configuration of the modified optical transmitter 2d, and the hardware configuration of the modified optical receiver 3d, respectively.

[0042] Some or all of the functional units of the optical communication device 101 are implemented as software by a processor 102, such as a CPU (Central Processing Unit), executing a program stored in a storage device 104 having a non-volatile recording medium (non-temporary recording medium) and a memory 103. The program may be recorded on a computer-readable non-temporary recording medium. A computer-readable non-temporary recording medium is, for example, a portable medium such as a flexible disk, magneto-optical disk, ROM (Read Only Memory), CD-ROM (Compact Disc Read Only Memory), or a storage device such as a hard disk built into a computer system. The communication unit 105 performs predetermined communication processing. The communication unit 105 may also acquire the program.

[0043] Some or all of the functional parts of the optical communication device 101 may be implemented using hardware including electronic circuits (or circuits) such as LSI (Large Scale Integrated Circuit), ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), or FPGA (Field Programmable Gate Array).

[0044] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention. [Industrial applicability]

[0045] This invention is applicable to optical communication systems (analog RoF (Radio-over-Fiber) systems) that convert input signals into optical analog signals and transmit them. [Explanation of symbols]

[0046] 1a, 1b, 1c, 1d... Optical communication system, 2a, 2b, 2c, 2d... Optical transmitting device, 3a, 3b, 3c, 3d... Optical receiving device, 4... Transmission path, 5... Control device, 21... Adding unit, 22... Light source unit, 23... Batch conversion unit, 31a, 31b, 31c... Optical filter, 32... Photoelectric conversion unit, 33... Distribution unit, 34... Detection unit, 100... Optical communication device, 101... Optical communication device, 102... Pro 103...Memory, 104...Storage device, 105...Communication unit, 110...Batch conversion unit, 111...Optical intensity modulation unit, 112...Photoelectric conversion unit, 113...Delay detection unit, 114...Amplification unit, 115...Phase modulation unit, 116...Addition unit, 117...First light source unit, 118...Multiplier unit, 119...Second light source unit, 120...Optical receiver unit, 121...Third light source unit, 221...Integration unit, 222...Phase modulation unit

Claims

1. A light source unit that generates output light of a predetermined wavelength, An integration unit that integrates the input signal, A phase modulation unit generates an optical frequency modulated signal by performing phase modulation on the output light using the integrated input signal, and outputs the generated optical frequency modulated signal to the transmission path. Equipped with, From the detection unit that detects the intensity of the electrical signal based on the transmitted optical frequency modulation signal, information corresponding to the intensity of the electrical signal is obtained. The light source unit generates output light of a predetermined wavelength, adjusted to increase the intensity of the electrical signal based on the acquired information. Optical transmission device.

2. An optical communication system comprising an optical transmitting device and an optical receiving device, The optical transmitting device is A light source unit that generates output light of a predetermined wavelength, An integration unit that integrates the input signal, The system includes a phase modulation unit that generates an optical frequency modulated signal by performing phase modulation on the output light using the integrated input signal, and outputs the generated optical frequency modulated signal to a transmission line. The aforementioned optical receiving device is An optical filter that generates an optical intensity modulated signal by performing slope detection processing on the optical frequency modulated signal transmitted through the transmission line based on the slope of the attenuation characteristics, A photoelectric conversion unit that converts the aforementioned light intensity modulated signal into an electrical signal, The system includes a detection unit that detects the intensity of the electrical signal, The optical transmitting device acquires information from the detection unit corresponding to the intensity of the electrical signal, The light source unit generates output light of a predetermined wavelength, adjusted to increase the intensity of the electrical signal based on the acquired information. Optical communication system.

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