JPH11186993A - Optical transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform transmission through an optical fiber of a narrow pass band by block-encoding a binary code of a specified but width, converting it into the binary code of a specified bit width larger than that, furthermore converting it to at least a ternary code and transmitting it. SOLUTION: A 4B5B code conversion part 102 converts a binary code of a 4-bit width outputted by a transmission control part 101 into a binary code of a 5-bit width by referring to a conversion table provided inside and performing block-encoding. The binary code is parallel/serial converted and then converted to a ternary code of the 5-bit width by a ternary code converter 110 composed of a pre-coder 104 and a transversal equalizer 105, and optical signals generated by an electro-optical conversion part 106 are emitted to a plastic optical fiber 3. A receiver 2 of a device constitution opposite to a transmitter 1 receives optical signals and decodes the binary code of the 4-bit width. The transmission light based on the multi-valued code has a moderate time fluctuations of power, spectrum of the optical signals of which is narrow and suitable for the plastic optical fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission system, and more particularly, to an optical transmission system in which an optical transmission device and an optical reception device are connected by an optical fiber, and an optical signal emitted from the optical transmission device is transmitted. The present invention relates to an optical transmission system in which light is transmitted on the optical fiber and received by an optical receiver.

[0002]

2. Description of the Related Art Some conventional optical transmission systems use a block code as a transmission line code. FIG.
ANSI (American National Standard Institute) X3T9.5
FIG. 2 is a block diagram illustrating a conventional optical transmission system configured based on a PHY. In FIG. 11, an optical transmission apparatus 1110 and an optical reception apparatus 1120 are connected to an optical transmission system via an optical fiber 1130 so as to enable optical transmission.

[0003] The optical transmitter 1110 includes a data generator 1.
111, a block encoder 1112, a parallel-serial converter 1113, an NRZ-NRZI converter 1114,
The electro-optical converter 1115 is communicably connected. The optical receiver 1120 includes a photoelectric conversion unit 11.
21, an NRZI-NRZ conversion unit 1122, a serial-parallel conversion unit 1123, a block decoding unit 1124, and a data processing unit 1125 are communicably connected. The optical fiber 1130 has a core diameter of 50 μm or 62.
Quartz GI with 5μm and cladding diameter of 125μm
A graded index optical fiber is used.

The operation of the optical transmission system having the above configuration will be described below. First, the data generation unit 1111 generates transmission data or a control code, which is a 4-bit parallel binary code, and outputs it to the 4-bit data bus 1116, and at the same time, transmits the transmission data transmitted on the data bus 1116. And outputs “0” and “1” to the control line 1117 as an identifier C / D for specifying the control code. More specifically, in an idle state in which valid transmission data to be transmitted has not been generated, the data generation unit 1111 generates an idle code 124 indicating that fact (see FIG. 12).
, And continues to output “1” as the identifier C / D. Then, when valid transmission data is generated, the data generation unit 1111 starts a delimiter (hereinafter referred to as SD (Starting Delimiter)) 1 which is a start code of the packet.
21, transmission data 122, and an end delimiter (hereinafter, referred to as ED (Ending Delimiter)) 123 (also referred to as FIG. 12), which is the end code of the packet. Data bus 1
Output to 116. In the following, the idle code 124,
SD 121 and ED 123 are collectively referred to as control codes. Therefore, the data generation unit 1111 performs the processing shown in FIG.
As shown in FIG. 7, in the time section in which the SD 121 and the ED 123 are output, “1” is output as the identifier C / D, and in the time section in which the transmission data 122 is output, the identifier C / D is output.
"0" is output as D.

The block encoder 1112 receives transmission data or control codes and their identifiers C / D from the data bus 1116 and the control line 1117. The block encoding unit 1112 is provided with a conversion table for 4B5B conversion in advance, and converts an input 4-bit parallel binary code (transmission data 122 or control code) into an input identifier C / D. The conversion is performed with reference to the conversion table and the parallel binary code having a 5-bit width. Also, when the above-mentioned instruction is continuously input from the data generation unit 1111, the block coding unit 1112
The idle code 124 (also a parallel 2 with a 5-bit width)
Value sign).

The parallel-serial converter 1113 converts the 5-bit parallel binary code input from the block encoder 1112 into a serial binary code, and outputs the serial binary code to the NRZ-NRZI converter 1114. The NRZ-NRZI conversion unit 1114 converts an input serial binary code into an NRZ (Non-Return to Zero) modulated electric signal (hereinafter abbreviated as “NRZ electric signal”).
The NRZ electric signal is regarded as NRZI (Non-Return
to Zero Inverted) modulated electrical signal (hereinafter referred to as “NR
ZI electrical signal ”), and then converts the signal to an electro-optical signal.
Output to 115. The electro-optical converter 1115 converts the input NRZI electric signal into an optical signal, and
Emitted to 130. A packet transmitted on the optical fiber 1130 has a format as shown in FIG. In FIG. 12, the packet is SD121
, Transmission data 122, and ED 123,
The idle code 124 is optically transmitted in the time period in which the packet optical transmission is not performed.

On the other hand, in the optical receiver 1120, the photoelectric conversion unit 1121 reconverts the optical signal incident from the optical fiber 1130 into an electric signal and outputs the electric signal to the NRZI-NRZ conversion unit 1122. The NRZI-NRZ conversion unit 1122 converts the input NR
The ZI electric signal is re-converted to the NRZ electric signal and serial-
Output to the parallel conversion unit 1123. The serial-parallel conversion unit 1123 converts the input serial binary code into N
The RZ electric signal is reconverted into a parallel binary code having a width of 5 bits and output to the block decoding unit 1124. The block decoding unit 1124 is provided with a conversion table for 5B4B conversion in advance, and converts the input 5-bit parallel binary code into
Referring to the conversion table, at the same time as converting to a 4-bit width parallel binary code and reproducing the identifier C / D (see above) for specifying transmission data or a control code, the parallel binary code is converted to 4 bits. The data is output to the data bus 1126 having the width, and the reproduced identifier C / D is output to the control line 1127. The data processing unit 1125 includes the data bus 112
6 and the control line 1127, when the 4-bit parallel binary code and the identifier C / D are input, the transmission data 122 based on the control codes SD121 and ED123.
And perform data processing such as separation.

By the way, as is well known, one condition required for a transmission line code is that codes having the same value are not excessively continuous. Therefore, the optical transmission device 1110
In this example, processing such as 4B5B conversion is performed so that the sign of the same value is not excessively continuous and the DC component is suppressed. That is,
Since the transmission data generated by the data generation unit 1111 is affected by data input by a user of the computer or the like, the same binary code may be excessively continuous.
Since the block encoding unit 1112 includes a conversion table created in advance for 4B5B conversion, even if all of the input parallel binary codes (transmission data or control codes) have the same value, for example, they may have different values. 5 is mixed moderately
It can be converted to a bit width parallel binary code.

Further, the optical transmittable frequency bandwidth of the optical transmission system shown in FIG. 11, the clock frequency in the form of the NRZI electrical signals from the NRZ-NRZI converter unit 1114 when the f _0, at least f ₀ / 2 (Nyquist frequency) bandwidth is required. However, even if the transmission bandwidth of the optical transmission system is set in accordance with the Nyquist frequency, in practice, the phase of the electric signal received by the optical receiver 1120 is rotated, and as a result, intersymbol interference occurs. Therefore, the electro-optical converter 111 on the optical transmission device 1110 side
5. As an overall frequency characteristic of the optical fiber 1130 and the photoelectric conversion unit 1121 on the optical receiver 1120 side, a bandwidth wider than the Nyquist frequency bandwidth is set, and cosine roll-off or the like is performed on the optical receiver 1120 side. In order to prevent the occurrence of intersymbol interference in the transmission path code.

[0010]

In recent years, a general optical transmission system using an optical fiber has been required to use a large-diameter plastic optical fiber or the like in order to reduce the cost. . Among such plastic optical fibers, a step index type all plastic fiber (APF), a plastic clad fiber (PCF), and the like are highly available and easily applied to an optical transmission system. However, the pass band width of the plastic optical fiber is relatively narrow, and has a characteristic that it becomes narrow in inverse proportion to the optical transmission distance. In the conventional optical transmission system, as described above, a transmission bandwidth wider than the Nyquist frequency is set, and an equalization process such as cosine roll-off is performed on the transmission line code, so that intersymbol interference is reduced. It does not occur on the receiving device 1120 side. However, when an optical fiber having a characteristic in which the pass bandwidth narrows in inverse proportion to the optical transmission distance is applied to the conventional optical transmission system, if an attempt is made to secure the transmission bandwidth to such an extent that intersymbol interference does not occur, it is not sufficient. There is a problem that it becomes difficult to optically transmit the distance.

Therefore, an object of the present invention is to provide an optical transmission system to which an optical fiber such as the above plastic optical fiber, which has a severe restriction on a frequency band in which light can be transmitted, can be applied. Another object of the present invention is to provide an optical transmission system to which the above-mentioned optical fiber can be applied and which does not cause an increase in delay time required for transmission of a transmission line code.

[0012]

According to a first aspect of the present invention, an optical transmitter and an optical receiver are connected by an optical fiber, and an optical signal emitted from the optical transmitter is transmitted to the optical fiber. An optical transmission system in which optical transmission is performed on an optical receiver and received by an optical receiver, wherein the optical transmitter performs block coding on a binary code having an m-bit width (m is a natural number) to be transmitted and performs n-bit width ( (n is a natural number larger than m), a block encoding unit that converts the binary code into a binary code, and a predetermined encoding is performed on the n-bit-width binary code converted by the block encoding unit, and the ternary code is expressed as a ternary code or more. A multi-level encoding unit that converts the multi-level code into an n-bit width multi-level code, and an electro-optical conversion on the multi-level code converted by the multi-level encoding unit to generate an optical signal. An electro-optical converter for emitting a signal to an optical fiber; Location comprises performs a predetermined process on the optical signal incident from the optical fiber, a receiver for receiving binary code of m-bit width to be received. According to the first aspect, the transmission optical signal is generated based on the multilevel code in which the time variation of the power is gradual. Therefore, the spectrum of the optical signal can be made narrower than the conventional one. As a result, an optical fiber having a characteristic that its pass band width is relatively narrow and narrows in inverse proportion to the optical transmission distance can be applied to the optical transmission system. Further, since the spectrum of the optical signal can be narrowed, a relatively low-speed light-emitting element can be used as the electro-optical conversion unit, thereby making it possible to construct an optical transmission system at low cost.

[0013] In a second aspect based on the first aspect, the encoding of the predetermined method performed by the multi-level encoding section is partial response encoding. According to the second aspect, by applying the known partial response encoding,
An optical transmission system can be easily constructed.

[0014] In a third aspect based on the second aspect, the multi-level encoding section includes a precoder for converting an n-bit binary code output from the block encoding section into an intermediate code, and an intermediate code output from the precoder. A partial response equalizer for converting a code into a multi-level code, thereby performing partial response coding. According to the third aspect, an optical transmission system can be easily constructed by applying a typical circuit that performs partial response encoding.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the optical receiver performs photoelectric conversion on an optical signal incident from an optical fiber, and performs serial multi-level conversion. A photoelectric conversion unit for converting to a code, and a serial multi-value code for converting the serial multi-value code re-converted by the photoelectric conversion unit into a serial binary code.
Value code conversion unit and serial 2 code converted by the binary code conversion unit.
Serial code for converting a value code into an n-bit width binary code
A parallel conversion unit and a block decoding unit that executes block decoding on the binary code having an n-bit width converted by the serial-parallel conversion unit and converts the binary code into a binary code having an m-bit width (m is a natural number). Further prepare. According to the fourth aspect, since an optical signal can be demodulated by a combination of known techniques, an optical transmission system can be easily constructed.

In a fifth aspect based on any one of the first to fourth aspects, the optical fiber is a large-diameter multimode optical fiber. According to the fifth aspect, an optical transmission system can be constructed at low cost by applying a large-diameter multimode optical fiber which is low in cost and highly available.

According to a sixth aspect of the present invention, an optical transmitting apparatus and an optical receiving apparatus are connected by an optical fiber, and an optical signal emitted from the optical transmitting apparatus is optically transmitted on the optical fiber and is transmitted to the optical receiving apparatus. In an optical transmission system to be received, an optical transmitting apparatus collectively executes block coding and multi-level coding on a binary code having an m-bit width (m is a natural number) to be transmitted, and A block / multi-level encoding unit for converting into a multi-level code having an n-bit width (n is a natural number greater than m) represented by a value or more; An optical-to-optical conversion unit that performs optical conversion to generate an optical signal, and emits the generated optical signal to an optical fiber, wherein the optical receiver performs a predetermined process on the optical signal incident from the optical fiber. To receive the m-bit wide binary code to be received. That a receiving unit. According to the sixth aspect, the transmission optical signal is generated based on the multi-level code in which the time variation of the power is gradual. Therefore, the spectrum of the optical signal can be made narrower than the conventional one. As a result, an optical fiber having a characteristic that its pass band width is relatively narrow and narrows in inverse proportion to the optical transmission distance can be applied to the optical transmission system. Further, since the spectrum of the optical signal can be narrowed, a relatively low-speed light-emitting element can be used as the electro-optical conversion unit, thereby making it possible to construct an optical transmission system at low cost. Further, since the block coding and the multi-level coding are collectively executed, the delay time required for transmitting the m-bit width binary code does not increase.

In a seventh aspect based on the sixth aspect, the block / multi-level encoding unit includes a conversion table in which a correspondence between a binary code having an m-bit width and a multi-level code having an n-bit width is described. Block coding and multi-level coding are collectively performed with reference to the conversion table. According to the seventh aspect, by applying the above conversion table, collective block coding and multi-level coding can be easily realized.

In an eighth aspect based on the sixth or seventh aspect, the optical receiver performs photoelectric conversion on an optical signal incident from the optical fiber to convert the optical signal into a serial multilevel code. A photoelectric conversion unit, a binary code conversion unit that converts a serial multi-level code reconverted by the photoelectric conversion unit into a serial binary code, and a serial code conversion unit that converts the serial multi-value code. A serial-parallel converter for converting a binary code into a binary code having an n-bit width, and performing block decoding on the binary code having an n-bit width converted by the serial-parallel converter, m
A block decoding unit that converts the code into a binary code having a bit width (m is a natural number). According to the eighth aspect, since an optical signal can be demodulated by a combination of known techniques, an optical transmission system can be easily constructed.

According to a ninth aspect, in any one of the sixth to eighth aspects, the optical fiber is a large-diameter multimode optical fiber. According to the ninth aspect, an optical transmission system can be constructed at low cost by applying a large-diameter multimode optical fiber which is low in cost and highly available.

[0021]

FIG. 1 is a block diagram showing a configuration of an optical transmission system according to a first embodiment of the present invention.
In FIG. 1, an optical transmission device 1 and an optical reception device 2 are connected to an optical transmission system via an optical fiber 3 so as to enable optical transmission.

The optical transmitter 1 includes a transmission controller 101,
The 4B5B code converter 102, the parallel-serial converter 103, the precoder 104, the transversal equalizer 105, and the electro-optical converter 106 are communicably connected. In particular, the transmission control unit 101 and the 4B5B code conversion unit 102 are connected by a 1-bit width control line 107 and a 4-bit width data bus 108, and
The code converter 102 and the parallel-serial converter 103 are connected by a 5-bit data bus 109. The precoder 104 and the transversal equalizer 1
05 constitutes the ternary code conversion unit 110 (see the dotted line). The optical receiving device 2 includes a photoelectric conversion unit 201.
, A binary code converter 202, a serial-parallel converter 203, a 5B4B code converter 204, and a reception controller 205 are communicably connected. In particular, the serial-parallel converter 203 and the 5B4B code converter 204
Are connected by a data bus 206 having a width of 5 bits,
The B4B code conversion unit 204 and the reception control unit 205 include a data bus 207 having a 4-bit width and a control line 20 having a 1-bit width.
8 are connected.

Hereinafter, the operation of the optical transmission system configured as described above will be described in more detail. Transmission control unit 101
Only when the packet 4 (see FIG. 2) is transmitted to the optical receiver 2, a start delimiter (Starting Delimiter; hereinafter, referred to as “SD”) 41 which is a start code of the packet 4 and the optical receiver 2 Transmission data 42 to be transmitted
And an end delimiter (Ending Delimiter; hereinafter referred to as “ED”) 43 which is an end code of the packet 4. When not transmitting the packet 4, the transmission control unit 101 keeps outputting the idle code 44 for indicating that the transmission control unit 101 is in the idle state. Therefore,
In this optical transmission system, the packet 4 optically transmitted on the optical fiber 3 has a format as shown in FIG.

In the present embodiment, the SD 41, the transmission data 42, the ED 43, and the idle code 44 are preferably represented by 4-bit parallel binary codes that do not overlap with each other. In this embodiment, for the sake of convenience, it is assumed that the SD 41 is represented by a combination of “J” and “K”, the ED 43 is represented by “T”, and the idle code 44 is represented by “I”. Further, SD41, ED43 and idle code 44 are collectively referred to as control code. Hereinafter, unless otherwise specified in the present embodiment, the parallel binary code has a 4-bit width.

The SD 41, transmission data 42, ED 43
And the idle code 44 are the data bus 1 having a 4-bit width.
08 to the 4B5B code conversion unit 102. Further, as shown in FIG. 2, the transmission control unit 101 specifies the transmission data 42 and the control code transmitted on the data bus 108, and outputs the transmission data 42 as an identifier C / D while outputting the transmission data 42. “0” is output to the control line 107 as the identifier C / D while the control code is being output. The 4B5B code conversion unit 102 is connected to the data bus 1
08 and a parallel binary code and an identifier C / D from the control line 107. The 4B5B code conversion unit 102 is provided with a conversion table 1021 as shown in FIG. 3 in advance, and converts the input 4-bit parallel binary code into the simultaneously input identifier C / D and the conversion table 1021. Is converted into a parallel binary code having a width of 5 bits, and
The data is output to a data bus 109 having a bit width. Here, there is a one-to-one correspondence between the 4-bit parallel binary code and the 5-bit parallel binary code, and the correspondence is described in the conversion table 1021 shown in FIG. . For example,
The parallel binary code “0000” as the transmission data 42 is
It is converted into a parallel binary code “11110” having a 5-bit width.

The parallel-serial conversion unit 103 has 4B
The parallel binary code having a 5-bit width converted by the 5B code conversion unit 102 is input from the data bus 109, converted into a serial binary code, and output to the ternary code conversion unit 110.

The ternary code conversion unit 110 performs a so-called partial response coding, thereby sequentially converting binary codes input serially into ternary codes. As described above, the ternary code conversion unit 110 includes the precoder 104
And a transversal equalizer 105. FIG. 4 is a block diagram showing a detailed configuration of the precoder 104 and the transversal equalizer 105. 4, first, the precoder 104 includes an Ex-Or adder 1041 and a delay unit 1042. Delay device 10
42 operates in synchronization with an internal clock, and Ex-Or
The output value of the adder 1041 (intermediate code described later) is delayed by one bit time and fed back to the Ex-Or adder 1041. The Ex-Or adder 1041 divides the binary code addition value input from the parallel-serial conversion unit 103 and the delay unit 1042 by “2”, and outputs the remainder. The remainder is an intermediate code for converting a binary code into a ternary code, and is input to the delay unit 1042 and the transversal equalizer 105. The transversal equalizer 105 includes a delay unit 1051 and an adder 1052. First, the intermediate code generated by the precoder 104 is
The signal is branched and input to the delay unit 1051 and the adder 1052. The delay unit 1051 operates in synchronization with the same clock as described above, delays the input intermediate code by one bit time, and outputs the result to the adder 1052. The adder 1052 is 2
An added value obtained by adding the intermediate code input after the branch and the intermediate code delayed by one bit by the delay unit 1051 is output. The added value output from the transversal equalizer 105 is a ternary code, and thus the ternary code conversion unit 110 converts a binary code into a ternary code.

FIG. 5 shows a control code and a 4B5B code corresponding to the transmission data 42 output by the transmission control unit 101.
FIG. 3 is a diagram illustrating output codes of a code conversion unit 102, a precoder 104, and a transversal equalizer 105. In FIG. 5, first, when the transmission control unit 101 is outputting “I” (idle code 44) (on the early side in the time axis), as can be seen from FIG. 3, the 4B5B code conversion unit 102 The bit width binary code "11111" is output. At this time, the precoder 104 converts the intermediate code “010
10 "and the transversal equalizer 105
Outputs a ternary code “11111”. It should be noted that the exemplary intermediate code and ternary code correspond to the delay unit 1 at the timing when the first bit (see the italic font in the figure) is input.
042 and 1051 are obtained on the assumption that the output values are “1”. In other words, depending on whether the above-mentioned first bit is “0” or “1”, the intermediate code or the ternary code output thereafter changes, but the entirety of the precoder 104 and the transversal equalizer 105 is changed. Since the operations are the same, only the case where the first bit is "1" is described. Thereafter, the transversal equalizer 105 outputs a ternary code as shown in FIG. 5 according to the output from the transmission control unit 101.

The electro-optical converter 106 (see FIG. 1) generates an optical signal by modulating the intensity of the internally generated unmodulated light with the ternary code input from the transversal equalizer 105. After that, the optical signal is emitted to the optical fiber 3.

FIG. 6 is a diagram for explaining the effectiveness of the optical transmission system according to the present embodiment with respect to a conventional optical transmission system. In FIG. 6, a spectrum 51 is shown.
(See the solid line part) is the spectrum of the optical signal generated based on the ternary code according to the present embodiment. A spectrum 52 (see a dashed line) is a spectrum of an optical signal generated based on a conventional binary code. First, the difference between the binary code and the ternary code will be described. The change of power with respect to time of the ternary code is more gradual than that of the binary code. Therefore, the optical signal based on the ternary code is spread within a narrower frequency band than the optical signal based on the binary signal, and more specifically, occupies only about half the frequency bandwidth.

Here, it is assumed that the optical fiber 3 is made of, for example, a large-diameter, multi-mode plastic optical fiber described in the section of the prior art. In this case, the optical fiber 3 has a relatively narrow pass band 53 (see a dotted line portion) as described above. Therefore, when a conventional optical signal (spectrum 51) is transmitted on the optical fiber 3 (passband 53), a phase distortion occurs in its waveform. As described in the section of the related art, it is practically impossible to completely equalize the optical signal in which the phase distortion has occurred on the optical receiving device 2 side. However, since the occupied frequency band of the optical signal (spectrum 51) of the present optical transmission system can be narrowed, the optical signal is hardly affected by the relatively narrow passband 53 and can be transmitted optically over a sufficient distance. Further, since the occupied frequency bandwidth of the optical signal to be optically transmitted can be narrowed like the spectrum 51, the electro-optical conversion unit 10
The light emitting element (not shown) provided inside 6 may be driven at a lower speed than in the past. Therefore, a light emitting element that is slower than the conventional light emitting element can be applied to the present optical transmission system. This can also reduce the cost of the optical transmission system.

As described above, the spectrum of the optical signal emitted from the electro-optical converter 106 is, as shown in FIG.
If the optical signal is within the pass band 53 of the optical fiber 3, the optical signal is incident on the photoelectric conversion unit 201 of the optical receiver 2 without being limited by the transmission distance due to the characteristics of the optical fiber 3. Further, even if the spectrum of the optical signal does not fall within the pass band 53 of the optical fiber 3 and is subject to band limitation, if the band limitation is such that no intersymbol interference occurs on the receiving device 12 side, the photoelectric conversion unit 201 In addition, the incident optical signal can be photoelectrically converted into a ternary code which is an electric signal. Thereafter, the photoelectric conversion unit 201 changes the ternary code to 2
Output to the value code converter 202.

If the input ternary code is "0" or "2", the binary code conversion unit 202 outputs "0" as the binary code, and outputs the binary code "1". , "1" is output as a binary code. The binary code re-converted according to the conversion rule from the ternary code to the binary code is output to the serial-parallel conversion unit 203. The serial-to-parallel converter 203 performs a serial-to-parallel conversion process on the serially input binary code,
The data is converted into a binary code having a bit width and output to a data bus 206 having a 5-bit width.

The 5B4B code conversion unit 204 has a conversion table 1021 shown in FIG.
It converts the 5-bit binary code input from 06 into a 4-bit parallel binary code (transmission data 42 or control code) and outputs it to the 4-bit data bus 207. 5
At the same time, the B4B code converter 204 reproduces the transmission data 42 or the identifier C / D (described above) for specifying the control code, and outputs the reproduced data to the control line 208 having a 1-bit width. Therefore, for example, a 5-bit binary code “1111”
0 ”is a parallel binary code“ 000 ”as the transmission data 42.
At the same time as being converted to "0", "1" is reproduced as the identifier C / D. The reception control unit 205 sends a parallel binary code and an identifier C / D from the data bus 207 and the control line 208.
Is input and the transmission data 42 is received according to the input control code while referring to the identifier C / D. As described above, in the present optical transmission system, the packet 4 is optically transmitted.

However, in the optical transmission system according to the above-described first embodiment, the delay unit 1042 shown in FIG.
Is delayed, and the delay unit 1051 further
The intermediate code input from the precoder 104 is delayed. As a result, the optical transmission system according to the first embodiment has a problem that a delay time required for optical transmission is increased. This problem is solved by the optical transmission system according to the second embodiment described below.

FIG. 7 is a block diagram showing the configuration of the optical transmission system according to the second embodiment of the present invention. In FIG. 7, an optical transmission system 6 and an optical reception device 7 are connected to an optical transmission system via an optical fiber 8 so as to enable optical transmission.

The optical transmitter 6 includes a transmission controller 61,
A B5B / 3-value code conversion unit 62, a parallel-serial conversion unit 63, and an electro-optic conversion unit 64 are communicably connected. In particular, the transmission control unit 61 and the 4B5B / 3-value code conversion unit 62 are connected by a 1-bit width control line 65 and a 4-bit width data bus 66, and the 4B5B / 3-value code conversion unit 62 and the parallel-serial conversion unit 63 is 5
They are connected by a data bus 67 having a bit width. The optical receiver 7 is connected to a photoelectric conversion unit 71, a binary code conversion unit 72, a serial-parallel conversion unit 73, a 5B4B code conversion unit 74, and a reception control unit 75. Have been. In particular, the serial-parallel converters 73 and 5
The B4B code converter 74 is a 5-bit data bus 76.
The 5B4B code converter 74 and the reception controller 75 are connected by a 4-bit data bus 77 and a 1-bit control line 78.

Hereinafter, the operation of the optical transmission system configured as described above will be described in more detail. Transmission control unit 61
Is the packet 4 shown in FIG. 2 as in the first embodiment.
Is transmitted to the optical receiver 7, the SD 41, the transmission data 42, and the ED 43 are output. Further, when not transmitting the packet 4, the transmission control unit 61 keeps outputting the idle code 44. These SD41, ED4
3 and the idle code 44 are collectively referred to as control codes as in the first embodiment. Therefore, also in the optical transmission system according to the present embodiment, the packet 4 optically transmitted on the optical fiber 3 has a format as shown in FIG. The transmission control unit 61 outputs the idle code 44, the SD 41, the transmission data 42, and the ED 43 to the 4-bit data bus 66. Further, as in the first embodiment, the transmission control unit 61 outputs “0” as the 1-bit identifier C / D while outputting the transmission data 42, and outputs the 1-bit identifier while outputting the control code. As "1"
Is output to the control line 65.

The 4B5B / 3-value code conversion unit 62 converts the first or second identifier C / D input from the control line 65,
Carry bit C1 held internally and conversion table 6
25, the parallel 2 input from the data bus 66.
The value code is collectively converted into a parallel ternary code having a 5-bit width. Hereinafter, such a batch conversion process is referred to as 4B5B / 3.
This is referred to as value code conversion processing. Here, FIG.
It is a figure showing the detailed composition of this 4B5B / 3 value code conversion part 62. In FIG. 8, the 4B5B / 3-value code conversion unit 6
2 is a register 621 to 624 and a conversion table 625
And The register 621 stores the parallel binary code input from the data bus 66. Register 622 is
A 5-bit parallel ternary code obtained by the 4B5B / 3-value code conversion process is stored. The register 623 stores the carry bit C1 which is referred to in the 4B5B / 3-value code conversion process for the currently input parallel binary code. The register 624 stores the carry bit C2 to be referred to for the 4B5B / 3-value code conversion processing for the next input parallel binary code. Hereinafter, the 4B5B / 3-value code conversion processing will be described in more detail.

For example, now, the transmission control unit 61
Are represented by a combination of “J” and “K” (see the first embodiment), and the parallel binary codes meaning “J” and “K” are sequentially output to the data bus 66. Assume that At this time, the transmission control unit 61 outputs “1” to the control line 65 as the identifier C / D. The parallel binary code meaning this “J” is a 4B5B / 3-ary code conversion unit 62
To the 4-bit register 621. At this time, the one carry bit C1 is the same as the previous 4B5B
"0" or "1" depending on the result of the ternary code conversion process
Is latched in the register 623. Below,
The case where the initial value of carry bit C1 is "0" will be described.

The 4B5B / 3 value conversion section 62 stores the register 6
Based on the parallel binary code being loaded and the identifier C / D inputted at the time of loading, it is recognized that the currently inputted one is the "J". After that, 4B5B /
In the ternary conversion unit 62, “J” is written in the column of 4B (parallel binary code having a 4-bit width) in the conversion table 625, and “0” is written in the column of the carry bit C1. After specifying the row, 5B (parallel 2 of 5 bit width)
The value “11000” written in the specified row in the “value code” column and the value “0” written in the specified row in the carry bit C2 column are extracted. The extracted 5-bit parallel binary code “1100
"0" is output to the data bus 67 after being loaded into the 5-bit register 622. “0” extracted as carry bit C 2 is latched by register 624.

Next, a parallel binary code meaning "K" is loaded into the register 621. In response to this load, the 4B5B / 3-value conversion unit 62 outputs the current register 624
Loads "0" into register 623 as carry bit C2 during latching. Thereafter, the 4B5B / 3-value conversion unit 62 executes the same processing as described above, so that the parallel ternary code “12221” having a 5-bit width is loaded into the register 622, and “0” is stored in the register 624 as the carry bit C2. Latched.

The above is the 4B5B / 3-value code conversion processing when the initial value of the carry bit C1 is "0" and the parallel binary codes are "J" and "K".
For other control codes and transmission data 42,
A similar 4B5B / 3-value code conversion process is performed. As described above, by the 4B5B / 3-ary code conversion process, the parallel binary code is collectively converted into a 5-bit parallel ternary code. In the partial response encoding process of the first embodiment, the precoder 104 and the transversal equalizer 1
The delay was given to the intermediate code in 05, but 4B
No delay is given in the 5B / 3-value code conversion process. Therefore, an increase in delay time required for optically transmitting the packet 4 does not occur.

The parallel-serial conversion unit 63 has a 4B5
The data is converted by the B / 3 ternary code conversion unit 62 and
7 is converted into a serial ternary code and output to the electro-optical converter 64. Electro-optical converter 64
Generates an optical signal by modulating the intensity of the internally generated unmodulated light with the serial ternary code input from the parallel-serial converter 63, and then emits the optical signal to the optical fiber 3. . The optical signal generated in this manner also has the effects described in the first embodiment with reference to FIG.

As described above, the optical signal emitted from the electro-optical converter 64 is transmitted via the optical fiber 8 and is incident on the opto-electric converter 71 of the optical receiver 7. The photoelectric conversion unit 71 photoelectrically converts the incident optical signal into a ternary code which is an electric signal, and converts the ternary code into a binary code conversion unit 7.
2 is output in series. The binary code conversion unit 72 converts the input ternary code into a binary code according to the conversion rule described in the first embodiment, and outputs the binary code to the serial-parallel conversion unit 73. The serial-parallel conversion unit 203 converts the binary code input in series into 5
The data is converted to a parallel binary code having a bit width and output to a data bus 206 having a 5-bit width.

The 5B4B code conversion section 74 is connected to the data bus 6
6 is converted into a control code or transmission data 4 which is a 4-bit parallel binary code.
2 and simultaneously reproduce the identifier C / D. Less than,
This conversion processing is referred to as 5B4B code conversion processing. Here, FIG. 9 is a diagram showing a detailed configuration of the 5B4B code conversion unit 74. In FIG. 9, the 5B4B code conversion unit 7
4 is a register 741 to 743 and a conversion table 744
And The register 741 stores a 5-bit parallel binary code input from the data bus 76. The register 742 stores a 4-bit parallel binary code (the transmission data 42 or the control code) obtained by the 5B4B code conversion process. The register 743 stores the 1-bit identifier C / D reproduced at the same time as the 5B4B code conversion processing. Hereinafter, the 5B4B code conversion processing will be described more specifically.

For example, it is assumed that the transmission control unit 61 sequentially transmits parallel binary codes representing “J” and “K” representing SD 41 in accordance with the above assumption. In this case, first, the parallel binary code “11” having a 5-bit width meaning “J” is used.
000 ”is loaded from the serial-parallel converter 73 to the register 741 of the 5B4B code converter 74 via the data bus 76. In response to this load, 5B4
The B code conversion unit 74 recognizes the 5-bit parallel binary code “11000” in the register 741, and
After specifying the row in which “11000” is written in the column of 5B in FIG. 44, the 4-bit width binary code “J” written in the specified row in the column of 4B, and the C / D
In the column of (identifier), “1” as the identifier C / D written on the same line is extracted. The extracted parallel binary code “J” and “1” as the identifier C / D
Is loaded onto the data bus 77 and the control line 78 after being loaded into the 4-bit register 742 and the 1-bit register 743. Next, the parallel binary code “10001” meaning “K” is loaded from the serial-parallel converter 73 to the register 741 of the 5B4B code converter 74 via the data bus 76. In response to this loading, the 5B4B code conversion unit 74 converts the conversion table 74
4 by performing the same 5B4B code conversion processing as described above, the parallel binary code “10” meaning “K” is obtained.
001 ”and“ 1 ”as the identifier C / D are stored in the register 7
After the data is loaded into the register 42 and the register 743, the data is output to the data bus 77 and the control line 78.

Upon receiving the parallel binary code and the identifier C / D from the data bus 77 and the control line 78, the reception controller 75 first receives the input identifier C / D based on the input identifier C / D. It is determined whether the parallel binary code is the transmission data 42 to be received or the control code, and the transmission data 42 or the control code is received. Thereafter, the reception control unit 75 receives the transmission data 42 to be received according to the received control code. As described above,
In this optical transmission system, the packet 4 is optically transmitted.

Next, the conversion table 62 on the optical transmitter 6 side
5 (see FIG. 8) and a conversion table 74 on the optical receiving device 7 side.
4 (see FIG. 9) will be described. It is assumed that the conversion table 744 is uniquely determined as shown in FIG. That is, in the conversion table 744, 4B
And 5B have a one-to-one relationship. Based on the conversion table 744 thus determined, the conversion table 6
25 is created as follows. Here, FIG.
FIG. 8 is a diagram for explaining a method of creating the conversion table 625.

FIG. 10A shows a precoder 81 and a transversal equalizer 82 similar to the configuration shown in FIG. The general operation of these precoder 81 and transversal equalizer 82 is the same as the configuration shown in FIG. 4 and will not be described here. And
As shown in the figure, the input to the Ex-Or adder 811 of the precoder 81 is X, and the output value of the precoder 81 is Y.
The output value of the delay unit 821 of the transversal equalizer 82 is Z, and the adder 822 of the transversal equalizer 82
Is set to Out.

As described above, the conversion table 744 is
Since 4B and 5B are created in advance so as to have a one-to-one relationship, the relationship between the first row 91 and the second row 92 shown in FIG. 10B, that is, a 4-bit width binary code ( The relationship between the transmission data 42 or the control code) and the 5-bit binary code (input value X to the precoder) is known. For example,
In the case of the control code “J”, the input value X is “110”.
00 ”has been determined. Here, when the initial value of the output value Z of the delay unit is “1” and the precoder 81 receives the binary code “11000” serially for each bit, the output value Y of the precoder 81 is output. Becomes “01111” as shown in the third row 93a of FIG. 10B, and as a result, the output value Out of the transversal equalizer 82 becomes
As shown in the fifth row 95a, it becomes "11222". On the other hand, when the initial value of the output value Z of the delay unit is “0” and the precoder 81 receives the binary code “11000” serially for each bit, the output value Y of the precoder 81 becomes , As shown in the sixth row 93b of FIG.
0000 ”, resulting in the transversal equalizer 8
2 is "1" as shown in the eighth row 95b.
1000 ".

The output value Out thus determined
(5-bit serial binary code) is described in the column of 5B in the conversion table 625. Also, the output value Z at that time
Are described in the same row in the conversion table 625 and in the column of C1. Then, the last bit of the output value Y (a 5-bit serial binary code) of the precoder 81, that is, the value of the bit surrounded by a square in the third row 93a or the sixth row 93b in FIG. Since it corresponds to the initial value of the output value Z of the delay unit for converting the next input value X into the output value Y, it is described in the column of C2 in the conversion table 625. FIG. 10B exemplifies the case of three types of transmission data 42 or control codes other than the control code “J”. Regarding these exemplified transmission data 42 or control codes, the output values Y, Z, and Out of each section are shown for the case where the initial value of the output value Z of the delay unit is “0” and “1”, respectively. Using these output values, the conversion table 625 on the optical transmitter 6 side is created.

In the optical transmission systems according to the first and second embodiments, the transmission data 22 and the control code have a 4-bit width, and the 4-bit parallel binary code has a 5-bit width. Had been converted. However, the present invention is not limited to this, and the transmission data 22 and the control code have an m-bit width, and the parallel binary code having the m-bit width has an n-bit width (n>
m). Furthermore, the first and second
In the optical transmission device of the optical transmission system according to the embodiment, 2
The value code was converted to a ternary code. However, the present invention is not limited to this, and the binary code may be converted to a ternary or higher code.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an optical transmission system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a format of a packet 4 optically transmitted on an optical fiber 3 in the optical transmission system shown in FIG.

FIG. 3 shows a 4B5B code converter 102 and 5B shown in FIG. 1;
Conversion table 10 provided inside 4B code conversion section 204
FIG.

FIG. 4 is a block diagram showing a detailed configuration of a precoder 104 and a transversal equalizer 105 shown in FIG.

FIG. 5 shows a 4B5B code conversion unit 10 corresponding to a control code and transmission data 42 output from a transmission control unit 101;
2. Precoder 104 and transversal equalizer 10
5 is a diagram showing an output code of No. 5. FIG.

FIG. 6 is a diagram for explaining the effectiveness of the optical transmission system according to the first embodiment with respect to a conventional optical transmission system.

FIG. 7 is a block diagram illustrating a configuration of an optical transmission system according to a second embodiment of the present invention.

8 is a diagram showing a detailed configuration of a 4B5B / 3-ary code conversion unit 62 shown in FIG.

9 is a diagram illustrating a detailed configuration of a 5B4B code conversion unit 74 illustrated in FIG. 7;

FIG. 10 is a diagram for explaining a method of creating the conversion table 625 shown in FIG.

FIG. 11 is a block diagram showing a conventional optical transmission system configured based on the ANSI X3T9.5 PHY standard.

FIG. 12 is a diagram showing a format of a packet optically transmitted on the optical fiber 113 shown in FIG. 11;

[Explanation of symbols]

1, 6: Optical transmission device 101, 61: Transmission control unit 102: 4B5B code conversion unit 62: 4B5B / 3-value code conversion unit 1021, 625, 744: Conversion table 103, 63: Parallel-serial conversion unit 104, 81: Precoders 1041, 811 Ex-Or adders 1042, 812 Delay devices 105, 82 Transversal equalizers 1051, 821 Delay devices 1052, 822 Adders 106, 64 Electro-optical conversion units 107, 65 Control Lines 108, 109, 66, 67 Data bus 110 Tri-state code converter 2, 7 Optical receiver 201, 71 Opto-electrical converter 202, 72 Binary code converter 203, 73 Serial-parallel conversion Units 204, 74 ... 5B4B code conversion units 205, 75 ... Reception control units 206, 207, 76, 77 ... 208, 78: Control line 3, 8, Optical fiber 4: Packet 621, 622, 623, 624, 741, 742, 7
43… Register

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // H03M 5/20 H04B 9/00 B

Claims (9)

[Claims] 1. An optical transmitter and an optical receiver are connected by an optical fiber, and an optical signal emitted from the optical transmitter is optically transmitted over the optical fiber and received by the optical receiver. A transmission system, wherein the optical transmitting apparatus performs block coding on a binary code having an m-bit width (m is a natural number) to be transmitted and converts the binary code into a binary code having an n-bit width (n is a natural number larger than m). Performing a predetermined encoding on the n-bit width binary code converted by the block encoding unit, and converting the n-bit width binary code into an n-bit width multi-level code represented by three or more values A multi-level encoding unit that performs an electro-optical conversion on the multi-level code converted by the multi-level encoding unit, generates an optical signal, and outputs the generated optical signal to the optical fiber. A light conversion unit, wherein the light receiving device comprises: An optical transmission system comprising: a receiving unit that performs a predetermined process on the optical signal incident from a fiber and receives the m-bit width binary code to be received. 2. The optical transmission system according to claim 1, wherein the encoding of the predetermined method performed by the multi-level encoding unit is partial response encoding. 3. The multi-level encoding unit includes: a precoder that converts the n-bit binary code output by the block encoding unit into an intermediate code; and a multi-level code that outputs the intermediate code output by the precoder. The optical transmission system according to claim 2, further comprising: a partial response equalizer configured to perform the partial response encoding. 4. The optical receiver, wherein the optical receiver performs optical-electrical conversion on the optical signal incident from the optical fiber to convert the optical signal into a serial multi-level code; A binary code conversion unit configured to convert the serial multi-level code re-converted by the conversion unit into a serial binary code; and the serial binary code converted by the binary code conversion unit, a serial-parallel converter that converts the binary code into an n-bit width binary code; and performs block decoding on the n-bit width binary code converted by the serial-to-parallel converter.
The optical transmission system according to any one of claims 1 to 3, further comprising: a block decoding unit that converts the binary code having a bit width (m is a natural number). 5. The optical transmission system according to claim 1, wherein said optical fiber is a large-diameter multimode optical fiber. 6. An optical transmitting apparatus and an optical receiving apparatus are connected by an optical fiber, and an optical signal emitted from the optical transmitting apparatus is optically transmitted on the optical fiber and received by the optical receiving apparatus. A transmission system, wherein the optical transmitter collectively executes block coding and multi-level coding on a binary code having an m-bit width (m is a natural number) to be transmitted,
A block / multi-level encoding unit for converting into a multi-level code having an n-bit width (n is a natural number greater than m) represented by three or more values; and a multi-level code converted by the block / multi-level encoding unit. An electrical-to-optical converter that generates an optical signal by performing electro-optical conversion on the optical fiber, and emits the generated optical signal to the optical fiber. An optical transmission system comprising: a receiving unit that executes a predetermined process on a signal and receives the m-bit width binary code to be received. 7. The block / multi-level encoding unit, wherein:
A conversion table in which a correspondence relationship between a binary code having a bit width and the multi-level code having the n-bit width is included in advance, and the block coding and the multi-level coding are collectively performed with reference to the conversion table. The optical transmission system according to claim 6, wherein the optical transmission system is executed. 8. The optical receiver, wherein the optical receiver performs photoelectric conversion on the optical signal incident from the optical fiber, and converts the optical signal into a serial multi-level code. A binary code conversion unit configured to convert the serial multi-level code re-converted by the conversion unit into a serial binary code; and the serial binary code converted by the binary code conversion unit, a serial-parallel converter that converts the binary code into an n-bit width binary code; and performs block decoding on the n-bit width binary code converted by the serial-to-parallel converter.
8. The optical transmission system according to 6 or 7, further comprising: a block decoding unit that converts a binary code having a bit width (m is a natural number). 9. The optical transmission system according to claim 6, wherein said optical fiber is a large-diameter multimode optical fiber.