JP2010068353A - Optical transmitting/receiving apparatus and single-core two-way optical transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively provide an optical transmission system for performing two-way full-duplex communication wherein transmission rates are asymmetric. <P>SOLUTION: A single-core two-way optical transmission system is provided which includes an optical transmitter and an optical receiver interconnected via a single-core optical cable 120. An E/O conversion unit 106 of the optical transmitter includes: a light-emitting section 201 for emitting transmission light modulated on the basis of transmission data; a light-receiving section 202 for performing optic/electric conversion on reception light received via the optical cable 120 and outputting the light; and a multiplexer/demultiplexer 203 for making the transmission light emitted form the light-emitting section 201 incident to an end face of the optical cable 120 and making the reception light emitted from the end face of the optical cable 120 incident to the light-receiving section 202. A spectral ratio of the transmission light and the reception light at the multiplexer/demultiplexer 203 is determined in accordance with a difference between transmission rates of transmission and reception signals. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical transmission / reception apparatus and a single-core bidirectional optical transmission system for bidirectional data transmission using an optical fiber cable.

As a method to realize bidirectional communication in optical fiber transmission capable of high speed and long distance transmission,
(A) a method of assigning two optical fibers for transmission and reception;
There are (b) a method in which transmission and reception are used in a time division manner with a single optical fiber, and (c) a method in which the wavelengths of transmission and reception are changed with a single optical fiber.

  In the case of transmitting video / audio signals to a display, recently, high-definition video and digitization of video are rapidly progressing, and high-speed and large-capacity data transmission is required. DVI (Digital Visual Interface) and HDMI (High-Definition Multimedia Interface) have come to be used as a transmission method that satisfies the performance required for such data transmission. In addition, when transmitting video signals from a personal computer, tuner, DVD player, etc. to a ceiling-type projector, it is necessary to transmit high-speed and large-capacity data over a long distance. May not be possible.

  As a solution to these problems, devices using optical fibers capable of high-speed and large-capacity data transmission as transmission media have begun to appear. Many of them are multi-core types that transmit electrical signals transmitted over DVI and HDMI wires as they are, and transmit optical modulation signals as they are. Since their diameter is 8 millimeters or more, they are quite thick cables and are used at home. It is not suitable for the routing of cables. Furthermore, since the cost of the electro-optical conversion unit is required for the number of channels, it is difficult to configure at low cost. In optical transmission, a light-emitting element that converts an electrical signal into light, a light-receiving element that converts light into an electrical signal, and respective electrical circuits are required. Therefore, reduction in the number of signals leads to cost reduction.

For this reason, a bidirectional optical transmission system capable of bidirectional full-duplex communication with a single optical fiber cable has been constructed to reduce the weight, flexibility, and cost of the cable (see, for example, Patent Documents 1 to 3). .
JP 2007-96733 A JP 2003-283438 A JP 2003-23400 A

  In the video signal transmission system as described above, a high-speed transmission is required to send a high-speed, large-capacity data signal like a high-definition video signal from an HDD recorder or the like to a display. From HDDs to HDD recorders, etc., there are only low-speed and small-capacity data signals such as displayable resolution information on the display and loopback of remote control signals, and high-speed transmission is not necessary.

  Therefore, allocating an optical fiber for low-speed data (the above-described optical transmission method (a)) increases the cost of the system. Furthermore, since it is necessary to always transmit the video signal, it is not desirable to switch between uplink and downlink by time division (optical transmission method (b)).

  In this way, in a single-core bidirectional optical transmission system that performs asymmetric optical communication, generally, the wavelength of the light emitting element for transmission and the sensitivity wavelength of the light receiving element for reception are set to different values, and the wavelength Optical interference between the transmission signal and the reception signal is reduced using a selection filter or the like (for example, see Patent Document 2). However, the wavelength selective filter is an expensive device, and it is necessary to align the optical axes of transmission and reception with high precision. It had become. Furthermore, since the emission wavelength changes depending on the environmental temperature, it is necessary to control the temperature of the element.

  In addition, a method has been proposed in which bidirectional communication is realized with a single optical fiber by changing the spectral ratio of a coupler that couples transmission and reception without using an expensive device, which is a wavelength selective filter ( For example, see Patent Document 3). However, although it is possible to reduce the light loss on the light receiving side by lowering the branching ratio on the light emitting side, the reception performance changes depending on the light emission power, and the transmission / reception performance cannot be optimized.

  Furthermore, a method for realizing bidirectional communication of asymmetric transmission rate data with a single optical fiber has also been proposed (for example, see Patent Document 1). Although there is a cost merit by using low-accuracy low-cost parts for the low-speed transmission unit, an external device for low-speed modulation and a controller are required.

  In general, in optical fiber transmission, expensive high-precision parts are used to ensure high-precision connection, and the unit price per channel is high. Thus, how to make an inexpensive system configuration with a small number of signal lines and connectors while taking advantage of the high speed of optical fiber transmission is a point to consider in mounting.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide an optical transmission / reception apparatus and a single-core bidirectional optical transmission system for performing bidirectional full-duplex communication, in which the transmission speed is asymmetric in each transmission direction. In the case where it is possible, an object is to provide an inexpensive optical transmission / reception apparatus and single-core bidirectional optical transmission system that enable high-speed and large-capacity data transmission with a small number of signal lines.

  In order to solve the above-described problem, the optical transmission / reception apparatus according to the first aspect of the present invention receives light from the outside via a light emitting unit that emits transmission light modulated based on transmission data and a single optical fiber cable. A light receiving unit that photoelectrically converts received light to output, and an optical combination that causes the transmitted light emitted from the light emitting unit to enter the end surface of the optical fiber cable and causes the received light emitted from the end surface to enter the light receiving unit. Including waver. The spectral ratio of the transmission light and the reception light in the optical multiplexer is determined according to the difference in transmission speed of the transmission / reception signal.

  According to the second aspect, in the optical transceiver, the spectral ratio between the transmitted light and the received light in the optical multiplexer is determined according to the difference in the required S / N ratio determined by the transmission speed of the transmitted / received signal.

  According to the third aspect, in the optical transceiver, the wavelengths of the transmitted light and the received light are made different.

  A fourth aspect of the present invention is a single-core bidirectional optical transmission system. This single-core bidirectional optical transmission system has a pair of optical transmission / reception devices interconnected by a single-core optical fiber cable. Each optical transmission / reception device includes: a light emitting unit that emits transmission light modulated based on transmission data; and a light receiving unit that photoelectrically converts received light received from the other optical transmission / reception device via the optical fiber cable and outputs the received light. And an optical multiplexer that causes the transmission light emitted from the light emitting portion to enter the end face of the optical fiber cable and causes the received light emitted from the end face to enter the light receiving portion. The spectral ratio of the transmission light and the reception light in the optical multiplexer is determined according to the difference in transmission speed of the transmission / reception signal.

  According to the fifth aspect, in the single-fiber bidirectional optical transmission system, the spectral ratio between the light emission signal and the light reception signal in the optical multiplexer is determined according to the difference in the required S / N ratio determined by the transmission speed of the transmission / reception signal. I made it.

  According to the sixth aspect, in the single-core bidirectional optical transmission system, the spectral ratio of the light emission signal and the light reception signal in the optical multiplexer is added to the difference in transmission speed of the transmission / reception signal, and The decision was made in consideration of the difference in the light emission power of the light emitting part.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the optical transmission / reception apparatus and single core bidirectional | two-way optical transmission system which perform bidirectional | two-way full-duplex communication whose transmission speed is asymmetrical are realizable.

<Embodiment 1>
With the spread of terrestrial digital broadcasting and the like, HD (High Definition) of video contents has progressed, and video display devices have become larger and higher definition, and device connection centering on large-screen TVs has become necessary. Such a video signal transmission system requires very high-speed transmission in order to send a high-speed, large-capacity data signal like a high-definition video signal from a content transmission source such as an HDD (Hard Disk Drive) recorder to a display. Is done. For this reason, wiring with metal cables has become difficult, and it is necessary to use thick, high-quality and expensive cables for long-distance wiring.

  As a video signal transmission method from the content transmission source to the display unit, DVI and HDMI are widely used. Both methods require a plurality of signals having a transmission rate exceeding 1 Gbps in order to transmit high-definition video. Furthermore, a plurality of low-speed data transmissions are required for device control and resolution information exchange.

  The embodiment of the present invention relates to a video transmission system utilizing the high speed of optical transmission and the high speed of data transmission in only one direction as described above, and will be described below with reference to FIGS. Details will be described.

  FIG. 1 is a configuration diagram of a single-core bidirectional optical transmission system according to the first embodiment. The optical transmitter 100 and the optical receiver 110 are interconnected via an optical cable 120.

  The video signal input unit 101 receives a video signal from a content transmission source such as an HDD recorder. In the case of an interface such as DVI or HDMI, a method called TMDS (Transition Minimized Differential Signaling) is adopted for transmission of a video signal. In TMDS, four channels are used for each link, and one channel is assigned to each of RGB of the video signal and one channel is assigned to the synchronizing signal of the clock frequency.

  Since the video signal transmitted by TMDS is different from a general LSI logic level as it is, it cannot be directly input except by a dedicated LSI. Therefore, the signal level conversion unit 102 converts the video signal input to the video signal input unit 101 into a signal level such as PECL (Positive Emitter Coupled Logic) or LVDS (Low Voltage Differential Signaling). Also, EMC (Electro-Magnetic Compatibility) countermeasure parts or the like may be mounted.

  Since the input signal data has a high data rate exceeding 1 Gbps, it is difficult to perform all signal processing such as multiplexing inside the LSI, and even if it can be realized, the LSI becomes expensive. Therefore, the serial / parallel converter 103 temporarily converts the serial input signal into a parallel signal, thereby reducing the signal data rate. At this time, the serial / parallel conversion unit 103 performs signal conversion as a simple data string without decrypting data encrypted for content protection in DVI or HDMI. This eliminates the need for new encryption or the like in the optical transmission unit, thereby reducing the price of the system and maintaining the stability of the system. It is also possible to provide a decryption circuit separately.

  The data signals parallelized by the serial / parallel converter 103 are three image data systems such as R, G, and B, and a clock signal. The multiplexing unit 104 performs signal processing such as multiplexing of video / audio signal data, multiplexing of data signals for low-speed bidirectional communication such as DDC (Display Data Channel) and CEC (Consumer Electronics Control), It is bundled so that it can be handled as a single high-speed data signal.

  The I / O processing unit 109 processes low-speed signal input / output signals that do not require parallel processing for reducing the data rate, such as DDC and CEC, and the input signal received by the E / O conversion unit 106 performs signal level conversion. The output signal is output to multiplexing section 104 to unit 102.

  The data signals bundled by the multiplexing unit 104 are converted into one system of high-speed serial data by the parallel / serial conversion unit 105. The data rate of the converted data signal does not necessarily need to be synchronized with the input signal clock of DVI or HDMI, and the DVI or HDMI signal clock information is also embedded in the multiplexing unit 104, thereby the parallel / serial conversion unit 105. There is a degree of freedom in the clock. As a result, it is possible to use existing parallel / serial conversion LSIs, and it is also possible to reduce the cost of the system by using general-purpose products without newly developing expensive high-speed parallel / serial conversion LSIs. Is possible.

  A signal converted into one system of high-speed serial data is input to the E / O converter 106. The E / O converter 106 converts the input electrical signal into an optical signal. The optical signal is transmitted to the O / E converter 116 of the optical receiver 110 via the optical cable 120.

  The O / E converter 116 converts the received high-speed serial data optical signal into a single electric signal. A single high-speed serial data signal is converted into a multiplexed parallel signal by the serial / parallel converter 115, and clock recovery is performed.

  The demultiplexing unit 114 receives multiplexed parallel signals, performs signal processing such as data separation of video / audio signals, and separation of data signals for low-speed bidirectional communication such as DDC and CEC, and R, G, B The three image data systems such as the above and the clock signal are restored.

  Further, the parallel / serial conversion unit 113 converts the parallel signal into a serial signal and outputs high-speed serial data according to DVI or HDMI. The signal level conversion unit 112 converts serial data into a TMDS signal level conforming to DVI or HDMI and outputs the signal level. The video signal output unit 111 outputs a video / audio signal to a display or the like.

  The I / O processing unit 119 processes low-speed input / output signals, and outputs the input signal received from the separation unit 114 to the signal level conversion unit 112 and the output signal to the O / E conversion unit 116, respectively.

  The clock changing unit 200 changes the clocks of the optical transmitter 100 and the optical receiver 110 according to the video transmission rate. For example, the transmitted video signal is an HD video, or SD (Standard Definition). The clock is adjusted according to whether the image is displayed. Each of the optical transmitter 100 and the optical receiver 110 has a function of adjusting the clock, and exchanges information via the I / O processing units 109 and 119 as one of the low speed information.

  FIG. 2 is a configuration diagram of the E / O conversion unit 106 of the optical transmitter 100 and the O / E conversion unit 116 of the optical receiver 110.

  The E / O conversion unit 106 includes a light emitting unit 201, a light receiving unit 202, a multiplexer / demultiplexer 203, and an optical I / F connector unit 204.

  The light emitting unit 201 converts high-speed serial data to be transmitted into an optical signal and emits transmission light. The light receiving unit 202 receives received light via the optical cable 120 and photoelectrically converts it into a low-speed data signal.

  The multiplexer / demultiplexer 203 bundles two optical signals of transmission light and reception light into one. Specifically, the multiplexer / demultiplexer 203 causes the transmission light emitted from the light emitting unit 201 to enter the end surface of the optical cable 120 connected to the optical I / F connector unit 204 and is emitted from the end surface of the optical cable 120. Received light is incident on the light receiving unit 202.

  Although the system can be configured even if the light emitted from the light emitting unit 201 and the light incident on the light receiving unit 202 have the same wavelength, the transmitted light and the received light may have different wavelengths.

  FIG. 3 is a diagram showing a specific configuration of the multiplexer / demultiplexer 203. The optical multiplexer / demultiplexer 203 may be an optical coupler for bundling two optical fibers into one as shown in FIG. 3A. As shown in FIG. The form using optical components, such as these, may be sufficient. Optical couplers are used in large quantities due to the widespread use of FTTH (Fiber To The Home), etc., and the price has been reduced. Furthermore, since they can be used as wiring materials in equipment, the E / O in the optical transmitter 100 can be used. There is a degree of freedom in the arrangement of the conversion unit 106. Thereby, it can contribute to size reduction of an apparatus, EMC countermeasures, etc.

  The spectral ratio in the multiplexer / demultiplexer 203 can be determined by the ratio between the high-speed transmission data transmission rate and the low-speed reception data transmission rate. This is because the S / N ratio necessary for data transmission has a parameter determined by the frequency band of the transmission signal, so that a higher S / N ratio is required as the data transmission speed increases. A method of setting the spectral ratio in the multiplexer / demultiplexer 203 will be described later.

  Returning to FIG. 2, the O / E conversion unit 116 of the optical receiver 110 includes a light receiving unit 211, a light emitting unit 212, a multiplexer / demultiplexer 213, and an optical I / F connector unit 214. The optical I / F connector unit 204 of the E / O conversion unit 106 on the optical transmitter 100 side and the optical I / F connector unit 214 of the O / E conversion unit 116 on the optical receiver 110 side are one optical cable 120. Are optically connected via

  In the optical receiver 110, DVI and HDMI signals are restored by the reverse data processing of the optical transmitter 100. The light receiving unit 211 receives received light via the optical cable 120 and photoelectrically converts it to high-speed serial data. The light emitting unit 212 converts a low-speed data signal to be transmitted into an optical signal and emits transmission light.

  The multiplexer / demultiplexer 213 bundles two optical signals of transmission light and reception light into one. Although the system can be configured even if the light emitted from the light emitting unit 212 and the light incident on the light receiving unit 211 have the same wavelength, the light may have different wavelengths.

  Here, since the light-emitting unit 212 on the optical receiver 110 side emits a low-speed signal, an infrared LED is used as a light-emitting device for low-speed, and the light-emitting unit 201 on the optical transmitter 100 side emits a high-speed signal. It is possible to use a long wavelength LD as a light emitting device for use. In that case, a low-speed signal is received on the optical transmitter 100 side, and a high-speed signal is received on the optical receiver 110 side, and each of the light receiving unit 202 of the optical transmitter 100 and the light receiving unit 211 of the optical receiver 110 is received. The wavelength sensitivity of the light receiving element is different. Therefore, a certain degree of wavelength separation is possible without using an expensive wavelength selection filter, and the system can be optimized by combining with the setting of the multiplexing / demultiplexing ratios of the multiplexers / demultiplexers 203 and 213.

Next, how to set the spectral ratio in the multiplexers / demultiplexers 203 and 213 will be described in detail.
The S / N ratio of the light receiver when the background light noise is not considered is defined by the following equation. Table 1 shows the received signal current and the noise power component.

  Table 2 shows an example of coefficient values and various parameter values.

In the case of a photodiode (PD), the circuit thermal noise dominates the S / N ratio, but in the case of an avalanche photodiode (APD), the effect of the circuit thermal noise is reduced by the effect of the multiplication factor, and the shot noise is dominant. You can see that In either case, the dominant component of the noise square term σ _D ² is proportional to the reception band B, and the reception signal current _SD does not depend on the reception band B. From this, it can be seen that when the reception band B is increased N times, the received signal is not changed, but the noise is increased N times.

  Generally speaking, in the case of data transmission by light intensity modulation, the S / N ratio at the light receiving unit is determined by received signal power, shot noise, dark current, circuit thermal noise, background light noise, etc. Although the factor for determining the S / N ratio differs depending on the type, the received signal power is not affected by the frequency band of data transmission. Therefore, it can be said that, generally, when the frequency band is increased N times, the noise becomes √N times.

  For example, when the high-speed data transmission rate is 1 GHz and the low-speed data transmission rate in the reverse direction is 10 MHz, the high-speed transmission reception band is 100 times the low-speed transmission reception band. An S / N ratio that is 10 times higher than that for low-speed transmission is required.

  Therefore, in the multiplexer / demultiplexers 203 and 213, the spectral ratio between the transmission light for high-speed data transmission transmitted from the optical transmitter 100 and the reception light for low-speed data transmission received by the optical receiver 110 is It can be determined by the ratio of the data rate to be transmitted. For asymmetric bidirectional data transmission such as high-speed video data transmission in the forward direction and low-speed control data transmission in the reverse direction, such as video transmission, the spectral ratio of the multiplexers / demultiplexers 203 and 213 is optimally set. By doing so, the quality of bidirectional data transmission can be made the same level. As a result, in an asymmetric bidirectional data transmission system using a single-core optical cable, the system can be configured without using an expensive configuration for wavelength separation, and high-speed, large-capacity data transmission can be achieved. It can be provided at low cost with quality.

  As described above, when the high-speed data transmission rate is 1 GHz and the low-speed data transmission rate in the reverse direction is 10 MHz, it is necessary to increase the S / N ratio of high-speed transmission 10 times. In this case, by setting the spectral ratio of the multiplexers / demultiplexers 203 and 213 to 76:24, as described below, the received light quantity ratio between the high speed transmission and the low speed transmission can be set to about 10: 1.

  For high-speed data transmission, the amount of transmission light emitted from the light emitting unit 201 of the E / O conversion unit 106 of the optical transmitter 100 is reduced to 76% by the multiplexer / demultiplexer 203 during transmission. At this time, the light is further reduced to 76% in the multiplexer / demultiplexer 213 of the O / E converter 116 of the optical receiver 110 and received by the light receiver 211. Since 0.76 × 0.76 = 0.5776, the amount of incident light to the light receiving unit 211 is about 58% of the amount of emitted light for high-speed data transmission.

  On the other hand, for low-speed data transmission, the amount of transmission light emitted from the light emitting unit 212 of the O / E conversion unit 116 of the optical receiver 110 is reduced to 24% by the multiplexer / demultiplexer 213 during transmission, At the time of reception, the light is further reduced to 24% in the multiplexer / demultiplexer 203 of the E / O conversion unit 106 of the optical transmitter 100 and received by the light receiving unit 202. Since 0.24 × 0.24 = 0.0576, the incident light quantity to the light receiving unit 202 is about 5.8% of the outgoing light quantity for low-speed data transmission.

  Accordingly, when the light emitting unit 201 on the high speed transmission side and the light emitting unit 212 on the low speed transmission side emit light with the same light amount, the ratio of the incident light amount to the light receiving unit 211 on the high speed receiving side and the light receiving unit 202 on the low speed receiving side. Is 58: 5.8 = 10: 1. In this way, by setting the S / N ratio required for high-speed data transmission to 10 times the S / N ratio required for low-speed data transmission, the quality of bidirectional data transmission is made the same level. Can do.

  Although the case where the light emitting unit 201 on the high-speed transmission side and the light emitting unit 212 on the low-speed transmission side emit light with the same light amount has been described above, the light emission amounts may be different from each other. For example, as the light emitting device of the light emitting unit 212 on the low speed side, it is assumed that an LED that has a low modulation speed but can generate a large light emission power is used. In that case, the light receiving unit in the entire transmission path is reduced by lowering the spectral ratio of high-speed data transmission because the light emission power of the light-emitting unit 212 on the low-speed transmission side is larger than the light emission power of the light-emitting unit 201 on the high-speed transmission side. 211, the ratio of the amount of light incident on the light receiving unit 202 can be made constant.

  For example, when the light emission power of the light emission unit 212 on the low-speed transmission side is twice the light emission power of the light emission unit 201 on the high-speed transmission side, the spectral ratio of the multiplexers / demultiplexers 203 and 213 is set to 82:18. As described above, when the light quantity ratio by the multiplexer / demultiplexer is approximately 20 times and the light emission power on the low speed side is twice the light emission power on the high speed side, the respective received light quantity ratios are approximately 10 to 1. can do.

  For high-speed data transmission, the amount of transmitted light emitted from the light emitting unit 201 is reduced to 82% by the multiplexer / demultiplexer 203 during transmission, and further reduced to 82% by the multiplexer / demultiplexer 213 during reception. It decreases and is received by the light receiving unit 211. Since 0.82 × 0.82 = 0.6724, the amount of incident light to the light receiving unit 211 is about 67% of the amount of emitted light for high-speed data transmission.

  On the other hand, for low-speed data transmission, the amount of transmission light emitted from the light emitting unit 212 is reduced to 18% by the multiplexer / demultiplexer 213 during transmission, and is further increased by 18 at the multiplexer / demultiplexer 203 during reception. % Is received by the light receiving unit 202. Since 0.18 × 0.18 = 0.0324, the amount of incident light to the light receiving unit 202 is about 3.24% of the amount of emitted light for low-speed data transmission.

  Here, since the light emission power of the light emitting unit 212 on the low speed transmission side is twice the light emission power of the light emitting unit 201 on the high speed transmission side, the amount of light incident on the light receiving unit 211 on the high speed reception side and the light receiving unit 202 on the low speed reception side. The ratio is 67: 3.24 × 2 = 67: 6.48≈10: 1.

  In the above example, the transmission speed ratio between the low-speed transmission side and the high-speed transmission side is 100 times (10 Mbps and 1 Gbps). However, in other cases, an optimum spectral ratio can be set with a magnification according to the speed ratio. Table 3 summarizes the spectral ratios for various transmission speeds and light emission ratios.

  In the above description, the spectral ratio of the multiplexer / demultiplexer 203 of the optical transmitter 100 and the spectral ratio of the multiplexer / demultiplexer 213 of the optical receiver 110 are set to the same value. The entire received light amount ratio may be set. For example, when the speed ratio between high-speed data transmission and low-speed data transmission is 100: 1, the spectral ratio of the multiplexer / demultiplexer 203 of the optical transmitter 100 is 91: 9, and the spectral ratio of the multiplexer / demultiplexer 213 of the optical receiver 110 is. Assuming that the ratio is 50:50, as will be described below, the received light quantity ratio can be 10: 1 in the entire system.

  For high-speed data transmission, the amount of transmitted light emitted from the light emitting unit 201 is reduced to 91% by the multiplexer / demultiplexer 203 during transmission, and further reduced to 50% by the multiplexer / demultiplexer 213 during reception. It decreases and is received by the light receiving unit 211. Since 0.91 × 0.5 = 0.455, the amount of incident light to the light receiving unit 211 is about 46% of the amount of emitted light for high-speed data transmission.

  On the other hand, for low-speed data transmission, the amount of transmission light emitted from the light emitting unit 212 is reduced to 50% by the multiplexer / demultiplexer 213 during transmission, and further 9 by the multiplexer / demultiplexer 203 during reception. % Is received by the light receiving unit 202. Since 0.5 × 0.09 = 0.045, the amount of incident light to the light receiving unit 202 is about 4.5% of the amount of emitted light for low-speed data transmission.

  Accordingly, when the light emitting unit 201 on the high speed transmission side and the light emitting unit 212 on the low speed transmission side emit light with the same light amount, the ratio of the incident light amount to the light receiving unit 211 on the high speed receiving side and the light receiving unit 202 on the low speed receiving side. Is 46: 4.5≈10: 1.

<Embodiment 2>
The data transmission rates of the parallel / serial conversion unit 105 and the E / O conversion unit 106 of the optical transmitter 100 of the first embodiment and the O / E conversion unit 116 and the serial / parallel conversion unit 115 of the optical receiver 110 are each 5 Gbps or more. Therefore, mounting difficulties may occur from the viewpoint of LSI cost, power consumption, and the like. In the second embodiment, these configurations are separated into two systems to lower the operating frequency and facilitate mounting. Since the other configuration is the same as that of the first embodiment, the description of the common configuration will be omitted by using the same reference numerals as those of the first embodiment, and the configuration and operation unique to the second embodiment will be described.

  The multiplexing unit 104 of the optical transmitter 100 according to the second embodiment performs signal processing such as multiplexing of video / audio signals, multiplexing of data signals for low-speed bidirectional communication such as DDC, and the like. The input signal is bundled so that it can be handled as a data signal. The parallel / serial conversion unit 105 converts the data signals bundled by the multiplexing unit 104 into two systems of high-speed serial data.

FIG. 4 is a configuration diagram of the E / O conversion unit 106 and the O / E conversion unit 116 according to the second embodiment. The E / O conversion unit 106 according to the second embodiment includes two light emitting units 201a and 201b corresponding to two systems of high-speed serial data. The need for wavelength separation, the wavelength lambda ₂ of the transmitted light that the first wavelength lambda ₁ of the transmission light emitting portion 201a is emitted second light emitting portion 201b is emitted are different. Wavelength lambda ₃ of the received light entering the light receiving portion 202, first either one wavelength lambda ₁ or the second light emitting portion 201b of the transmission light emitting portion 201a is emitted is the wavelength lambda ₂ of the transmitted light emitted bets May be equal.

  The multiplexer / demultiplexer 203 bundles two optical signals, which are two transmission lights having different wavelengths emitted from the two light emitting units 201 a and 201 b and three received light signals incident on the light receiving unit 202, into one. The optical I / F connector unit 204 of the E / O conversion unit 106 and the optical I / F connector unit 214 of the O / E conversion unit 116 are connected by a single optical cable 120.

The O / E conversion unit 116 according to the second embodiment receives two light receiving units 211a and 211b corresponding to the two light emitting units 201a and 201b of the E / O conversion unit 106 in order to receive two systems of high-speed serial data. Have The wavelength of the received light incident on the first light receiving unit 211a is λ ₁ , and the wavelength of the received light incident on the second light receiving unit 211b is λ ₂ . Wavelength of transmitted light that the light emitting unit 212 emits light for low speed data transmission is lambda _3. The multiplexer / demultiplexer 213 bundles two reception lights and one transmission light into one.

  In this way, the high-speed serial data optical signal received by the O / E converter 116 is converted into two systems of electrical signals and supplied to the serial / parallel converter 115. The two systems of high-speed serial data are converted into multiplexed parallel signals by the serial / parallel converter 115 of the optical receiver 110, and clock recovery is performed.

<Embodiment 3>
In the configuration in which high-speed serial data is separated into two systems as in the second embodiment, transmission is performed with two optical fibers connecting the E / O conversion unit 106 and the O / E conversion unit 116 instead of one. You can also. Embodiment 3 has a configuration in which two systems of high-speed serial data are transmitted using two optical fiber cables. The configurations of the E / O conversion unit 106 and the O / E conversion unit 116 are different from those of the second embodiment. Since other configurations are the same as those of the second embodiment, description thereof is omitted.

  FIG. 5 is a configuration diagram of the E / O conversion unit 106 and the O / E conversion unit 116 according to the third embodiment. The E / O converter 106 of the optical transmitter 100 and the O / E converter 116 of the optical receiver 110 are interconnected by two optical cables 120a and 102b. Two optical I / F connector sections 204a and 204b are connected to the E / O conversion section 106, and two optical I / F connector sections 214a and 214b are connected to the optical cables 120a and 120b. Provided for.

The E / O conversion unit 106 includes two light emitting units 201a and 201b for transmitting two systems of high-speed serial data. The transmission light having the wavelength λ ₁ emitted from the first light emitting unit 201a is incident on the first optical cable 120a connected to the first optical I / F connector unit 204a.

The transmission light having the wavelength λ ₁ emitted from the second light emitting unit 201 b is input to the multiplexer / demultiplexer 203. The multiplexer / demultiplexer 203 bundles the transmission light having the wavelength λ ₁ emitted from the second light emitting unit 201 b and the reception light having the wavelength λ ₂ incident on the light receiving unit 202 into one. The wavelength λ _{1 of the} transmission light emitted from the second light emitting unit 201 b and the wavelength λ _{2 of the} received light incident on the light receiving unit 202 may be the same.

  The multiplexer / demultiplexer 203 is connected to the second optical I / F connector unit 204b, makes the transmission light emitted from the second light emitting unit 201b incident on the end surface of the second optical cable 120b, and the second optical I / F connector unit 204b. Received light emitted from the end face of the optical cable 120 b is incident on the light receiving unit 202.

  Since the transmission light from the first light emitting unit 201a and the transmission light from the second light emitting unit 201b are incident on different optical cables 120a and 120b, the wavelengths of these two transmission lights may be the same.

The O / E conversion unit 116 of the optical receiver 110 has two light emitting units 201a and 201b corresponding to the two light emitting units 201a and 201b of the E / O conversion unit 106 of the optical transmitter 100 in order to receive two systems of high-speed serial data. It has the light-receiving parts 211a and 211b. The first light receiving unit 211a receives the reception light having the wavelength λ ₁ emitted from the first optical cable 120a connected to the first optical I / F connector unit 214a.

The transmission light having the wavelength λ ₂ emitted from the light emitting unit 212 is input to the multiplexer / demultiplexer 213. The multiplexer / demultiplexer 213 bundles the transmission light having the wavelength λ ₂ emitted from the light emitting unit 212 and the reception light having the wavelength λ ₁ incident on the second light receiving unit 211b.

  The multiplexer / demultiplexer 213 is connected to the second optical I / F connector portion 214b, and causes the transmission light emitted from the light emitting portion 212 to enter the end surface of the second optical cable 120b and the second optical cable 120b. The received light emitted from the end face is incident on the second light receiving portion 211b.

<Embodiment 4>
FIG. 6 is a configuration diagram of a single-core bidirectional optical transmission system according to the fourth embodiment. The optical transmitter 100 is provided with a network signal input unit 107 and a physical layer device 108, and the optical receiver 110 is different from the first embodiment in that a network signal output unit 117 and a physical layer device 118 are provided. Since other configurations are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and description thereof is omitted.

  The network signal input unit 107 has, for example, an RJ45 connector for Ethernet (registered trademark), and receives data transmitted / received via the network. Transmission / reception data is converted into a signal-processable format by the physical layer device 108 and supplied to the signal level conversion unit 102. The transmission / reception data is multiplexed together with the video / audio signal by the multiplexing unit 104. Since the video data signal has a bit rate exceeding 5 Gbps, for example, even if a 100 Mbps Ethernet (registered trademark) signal is multiplexed, the increased bit rate is 10% or less, and the influence on the optical transmission performance is small.

  The separation unit 114 of the optical receiver 110 receives the multiplexed parallel signal from the serial / parallel conversion unit 115, performs data separation of video / audio signals, separation of data signals for low-speed bidirectional communication such as DDC, and the like. In addition to performing signal processing, the network transmission / reception data is also separated.

  The network transmission signal is converted into a desired data transmission / reception format by the physical layer device 118 and supplied to the network signal output unit 117. The network signal output unit 117 has an RJ45 connector for Ethernet (registered trademark) as an example, and inputs data transmitted / received via the network.

  In the fourth embodiment, the high-speed serial data signal described in the second embodiment is separated into two systems, or two high-speed serial data signals are transmitted using the two optical fiber cables described in the third embodiment. A transmission structure may be used.

  The single fiber bidirectional optical transmission system according to the embodiment of the present invention has the following effects. When paying attention to the difference in the transmission speed of bidirectional communication, the required S / N differs depending on the required transmission speed. Therefore, the low-speed transmission path has the same transmission quality with less light than the high-speed transmission path. Can be secured. Therefore, the system can be optimized by setting the spectral ratio so as to obtain the S / N ratio corresponding to the transmission speed and selecting the light emitting / receiving device.

  Furthermore, since the light emitting / receiving device on the low speed side does not require a response speed, a light emitting / receiving element having a relatively large area can be used. Therefore, component accuracy and positioning accuracy are eased, and system cost can be reduced in addition to device cost. . That is, according to the embodiment of the present invention, using a simple optical multiplexer / demultiplexer, the spectral ratio is set according to the transmission speed of the transmission signal, and a high-speed / large-capacity transmission signal, A small-capacity transmission signal can be transmitted efficiently and with high quality.

  The present invention has been described based on the embodiments. The embodiments are exemplifications, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are within the scope of the present invention. .

1 is a configuration diagram of a single-core bidirectional optical transmission system according to Embodiment 1. FIG. It is a block diagram of the E / O conversion part and O / E conversion part of FIG. It is a figure which shows the specific structure of the multiplexer / demultiplexer of FIG. 6 is a configuration diagram of an E / O conversion unit and an O / E conversion unit of a single-core bidirectional optical transmission system according to Embodiment 2. FIG. 6 is a configuration diagram of an E / O conversion unit and an O / E conversion unit of a single-core bidirectional optical transmission system according to Embodiment 3. FIG. 6 is a configuration diagram of a single-core bidirectional optical transmission system according to Embodiment 4. FIG.

Explanation of symbols

  100 optical transmitter, 101 video signal input unit, 102 signal level conversion unit, 103 serial / parallel conversion unit, 104 multiplexing unit, 105 parallel / serial conversion unit, 106 E / O conversion unit, 107 network signal input unit, 108 Physical layer device, 109 I / O processing unit, 110 optical receiver, 111 video signal output unit, 112 signal level conversion unit, 113 parallel / serial conversion unit, 114 separation unit, 115 serial / parallel conversion unit, 116 O / E Conversion unit, 117 network signal output unit, 118 physical layer device, 119 I / O processing unit, 120 optical cable, 200 clock changing unit, 201 light emitting unit, 202 light receiving unit, 203 multiplexer / demultiplexer, 204 optical I / F connector unit 211 light receiving unit, 21 Emitting unit, 213 Go demultiplexer, 214 optical I / F connector.

Claims (6)

A light emitting unit for emitting transmission light modulated based on transmission data;
A light receiving unit that photoelectrically converts received light received from the outside via a single optical fiber cable, and
An optical multiplexer that causes the transmission light emitted from the light emitting unit to enter the end surface of the optical fiber cable, and that causes the received light emitted from the end surface to enter the light receiving unit,
An optical transmission / reception apparatus characterized in that a spectral ratio of transmission light and reception light in the optical multiplexer is determined according to a difference in transmission speed of transmission / reception signals.   The optical transmission / reception apparatus according to claim 1, wherein a spectral ratio between transmission light and reception light in the optical multiplexer is determined according to a difference in required S / N ratio determined by a transmission speed of transmission / reception signals.   3. The optical transmission / reception apparatus according to claim 1, wherein wavelengths of the transmission light and the reception light are made different. Having a pair of optical transceivers interconnected by single fiber optic cables;
Each optical transceiver is
A light emitting unit for emitting transmission light modulated based on transmission data;
A light receiving unit that photoelectrically converts and outputs the received light received from the other optical transceiver via the optical fiber cable;
An optical multiplexer that causes the transmission light emitted from the light emitting unit to enter the end surface of the optical fiber cable, and that causes the received light emitted from the end surface to enter the light receiving unit,
A single-fiber bidirectional optical transmission system characterized in that a spectral ratio of transmission light and reception light in the optical multiplexer is determined according to a difference in transmission speed of transmission / reception signals.   5. The single-core bidirectional light according to claim 4, wherein a spectral ratio between the light emission signal and the light reception signal in the optical multiplexer is determined according to a difference in required S / N ratio determined by a transmission speed of a transmission / reception signal. Transmission system.   The spectral ratio between the light emission signal and the light reception signal in the optical multiplexer is determined in consideration of the difference in the light emission power of the light emitting unit of each optical transmission / reception apparatus in addition to the difference in the transmission speed of the transmission / reception signal. The single-fiber bidirectional optical transmission system according to claim 4 or 5.