JPH04304044A - Timing signal distribution system - Google Patents

Abstract

PURPOSE:To prevent degrading of quality of a data signal in a subscriber transmission system by using an extracted timing signal for an input waveform shaping circuit use timing signal and a timing output signal of an optical subscriber system two-way transmitter. CONSTITUTION:A data signal fed to an optical transmitter 2 is a data signal DATA2 outputted from a terminal interface device 3 and a timing signal is a timing signal CLK1 extracted by an optical receiver 1. Thus, the characteristic of the waveform shaping timing signal CLK1 inputted to the optical transmitter 2 is not effected by a jitter production cause in the terminal interface device 3 and depends almost on the timing extraction characteristic of the optical receiver 1. Thus, the timing signal CLK1 with less jitter and having no high frequency noise is used to implement waveform shaping to the data signal DATA2, then the data signal with less jitter is generated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a timing signal distribution system in an optical subscriber bidirectional transmission system, and more particularly to a timing signal distribution system that makes it possible to prevent deterioration in transmission line quality.

0002

[Prior Art] Optical communication systems using optical fibers, which have excellent features such as low loss and broadband performance, have been introduced mainly in the backbone systems of public communication networks, and have a long distance speed of 1.6 Gbit/s. Large capacity system (F1.6G optical transmission system)
It has already been put into practical use (for example, described in Nikkei Electronics no. 432).

Furthermore, in recent years, with the development of optical transmission technology as described above, the application of optical transmission technology to subscriber transmission systems is being considered for the purpose of providing broadband communication services. In order to popularize and develop such optical subscriber system transmission equipment, it is essential to provide flexible services without deteriorating the quality of high-quality audio and image information.

An example of the configuration of an optical subscriber system that enables such flexible services is shown in FIG. This optical subscriber system includes, for example, a switch circuit 11 for switching channels of distributed video signals between a station building 7, a CATV center 8, and a subscriber premises equipment 10.
, a multiplexing/demultiplexing circuit 12 for multiplexing and demultiplexing data signals, an optical/electrical/electrical/optical converting circuit 13, etc., are arranged. In this configuration, the data signals sent from the subscriber premises equipment 10 to the remote multiplexer 9 are multiplexed by the multiplexing/demultiplexing circuit 12 in the remote multiplexer 9 and transmitted to the station 7, and the data signals from the station 7 are The multiplexing/demultiplexing circuit 12 in the remote multiplexer 9 separates the signal and transmits it to the subscriber's home equipment 10, and the switch circuit 11 switches the distribution video signal from the CATV center 8 and distributes it to the subscriber's home equipment 10. can. This makes it possible to flexibly provide services such as audio and image information from the station building 7 and the CATV center 8 to the subscriber's home equipment 10.

Note that in FIG. 4, the remote multiplexer 9 is
In addition to the multiplexing/demultiplexing circuit 12, the configuration includes a switch circuit 11 for switching channels of distributed video signals, for example. In some cases,

[0006] Here, the optical subscriber system transmission equipment is applied between the subscriber premises equipment 10 and the remote multiplexer 9, and between the remote multiplexer 9 and the office building 7, thereby providing broadband two-way communication services. is realized.

[0007] An optical transmission device applied to such an optical subscriber system generally has a configuration as shown in FIGS. 5 and 6. Here, FIG. 5 shows the optical receiver 1, and FIG. 6 shows the optical transmitter 2.

In FIG. 5, the optical receiver 1 includes a light receiving element 14
, an equalization amplifier circuit 15, a timing signal extraction circuit 16, and an identification reproduction circuit 17. An optical data signal (for example, transmission speed 600 Mbps) inputted to this optical receiver 1 from an opposing optical transmission device is transmitted to the light receiving element 1.
After being subjected to optical/electrical conversion by 4, it is amplified and shaped by an equalization amplifier circuit 15 into a waveform suitable for identification. The output signal of this equalization amplifier circuit 15 is branched into two, one of which is input to a timing signal extraction circuit 16. Then, a timing signal CLK1 (600 Mbps) synchronized with the transmission line speed
is extracted and output to the identification and reproduction circuit 17. Further, the other signal branched into two (the output signal of the equalization amplifier circuit 15) is inputted to the identification/reproduction circuit 17, and its waveform is identified using the timing signal CLK1 mentioned above. As described above, the input optical data signal is the data signal DATA1 (6
00Mbps).

Further, in FIG. 6, the optical transmitter 2 is composed of an input waveform shaping circuit 18, a light emitting element driving circuit 19, and a light emitting element 20. The data signal DATA2 (600 Mbps) input to the optical transmitter 2 is waveform-shaped by an input waveform shaping circuit 18 composed of, for example, a flip-flop and a buffer using the input waveform shaping timing signal CLK2, and then emitted. Element drive circuit 19
The current waveform is converted into a current waveform and applied to the light emitting element 20. As a result, the data signal DATA2 is subjected to electrical/optical conversion and is output to the opposing optical transmission device.

An optical subscriber system (FIG. 4) constructed using the optical transmission apparatus shown in FIGS. 5 and 6 generally employs a timing signal distribution system as shown in FIG.

In FIG. 7, data signal DATA1 (6
00Mbps) and timing signal CLK1 (600Mbps) extracted by the timing signal extraction circuit and synchronized with the transmission speed.
Mbps) is output to the terminal interface device 3 connected to the optical subscriber system bidirectional transmission device 5. In the terminal interface device 3, the input data signal DAT
A1 and the timing signal CLK1 are converted into signals suitable for the signal speed in the terminal device 4 and output to the terminal device 4. In addition, the low-speed data signal (150 Mbps) output from the terminal device 4 is processed by the terminal interface device 3, and the data signal DATA2 (600 Mbps) is processed by the terminal interface device 3.
s) and input waveform shaping timing signal CLK2 (600
Mbps) and input to the optical transmitter 2.

Generally, the signal speed at the terminal device 4 is lower than the transmission line speed (for example, 150 Mbps), so the terminal interface device 3 transfers the high-speed timing signal CLK1 outputted from the optical receiver 1, for example, to the terminal interface. A frequency dividing circuit that lowers the frequency to the frequency required for signal processing in the device 3 and the terminal device 4, and a frequency divider circuit that lowers the frequency to the frequency required for signal processing in the terminal interface device 3 and the terminal device 4, and lowers the frequency to a high frequency that is equal to the transmission path speed. It has a built-in frequency multiplier circuit.

As described above, in the conventional timing signal distribution system, the terminal interface device 3
The low-speed timing signal is increased in frequency using a frequency multiplier circuit in the optical transmitter 2, and is supplied as the input waveform shaping timing signal CLK2 required by the optical transmitter 2.

[0014]

[Problems to be Solved by the Invention] In the conventional timing signal distribution system in the subscriber transmission system, for example, by increasing the frequency of the low-speed timing signal in the terminal interface device, the timing signal for waveform shaping required in the optical transmission circuit is was generating. In order to achieve such a high frequency, for example, a frequency multiplier circuit built into a terminal interface device is used.

In addition to the frequency multiplication circuit, the terminal interface device may also include a data signal multiplexing/demultiplexing circuit, a switch circuit for switching channels of distributed video signals, and the like.

[0016] In such a circuit, there are influences due to noise components of the devices themselves used in the circuit, influences due to fluctuations in the operating point of the device mainly caused by external factors such as temperature fluctuations, and fluctuations in the IC used. Due to the effects of crosstalk between wires and wires within a circuit board, jitter in data signals and input waveform shaping timing signals input to the optical transmitter tends to increase.

Furthermore, in addition to jitter, noise may also occur in multiplexing/separating circuits built into terminal interface devices and the like. As an example, FIG. 8 shows the spectrum of the input timing signal of the multiplexing/demultiplexing circuit, and FIG. 9 shows the spectrum of the output timing signal. From FIG. 9, many noise signal components appear in the spectrum of the output timing signal of the multiplexing/demultiplexing circuit in addition to the timing signal component at the fundamental timing frequency (f0) and the second high frequency (2f0) noise signal component. . Therefore, when a multiplexing/demultiplexing circuit is used in which the spectral characteristics of the output timing signal are as shown in FIG. 9, the effects of high frequency noise are superimposed in addition to the effects of jitter.

If such jitter increases and a timing signal containing high-frequency noise is supplied to the optical transmitter for input waveform shaping, jitter and high-frequency noise will also occur in the waveform-shaped data signal. There was a problem in that the quality of transmitted data, audio, images, etc. deteriorated.

Furthermore, in the configuration example of the optical subscriber system shown in FIG. 4, the number of subscribers accommodated in the remote multiplexing device generally reaches several hundred. Against this background, when the conventional timing signal distribution method shown in Fig. 3 is applied to the optical subscriber system shown in Fig. 4, the multiple input signals input from the subscriber premises equipment to the remote multiplexing equipment are For the reasons stated above, each contains jitter. In such a case, jitter can be absorbed by comparing the phases of input and output signals using, for example, an elastic memory and achieving phase synchronization. However, when the number of subscribers accommodated in a remote multiplexing device reaches several hundred, the required memory capacity becomes enormous. Therefore, there is a limit to the ability of the remote multiplexer to absorb jitter, resulting in a problem of degrading the quality of the transmission path between the remote multiplexer and the station.

As described above, when using the conventional timing signal distribution system shown in FIG. Supplied from the terminal interface device. Therefore, this timing signal has
The effects of jitter and high frequency noise occur, and therefore, there is a risk that the quality of the timing signal whose waveform has been shaped using this timing signal may also be degraded. As mentioned above, conventional timing signal distribution systems have problems to be solved regarding jitter and high frequency noise.

An object of the present invention is to solve such conventional problems, and to improve data, voice, and data transmitted in a subscriber transmission system.
An object of the present invention is to provide a timing signal distribution method that makes it possible to prevent deterioration in the quality of images and the like.

[0022]

[Means for Solving the Problem] In order to solve the above-mentioned problem, the first invention of the present application provides an optical transmitter that transmits an optical signal to an opposing optical transmission device, and an optical transmitter that transmits an optical signal to an opposing optical transmission device. A timing signal distribution system in an optical subscriber system bidirectional transmission device having an optical receiver for receiving an optical signal from the device, the optical transmitter including an input waveform shaping circuit and an output of the input waveform shaping circuit. a light emitting element drive circuit that amplifies the
The optical receiver includes at least a light emitting element that emits light according to the output of the light emitting element drive circuit, and the optical receiver includes a light receiving element, an equalizing amplifier circuit that equalizes and amplifies the output of the light receiving element, and
a timing signal extraction circuit that extracts a timing signal from the output of the equalization amplifier circuit; and an identification and regeneration circuit that identifies and reproduces the output signal of the equalization amplifier circuit based on the timing of the timing signal output from the timing signal extraction circuit. The timing signal extracted by the timing signal extraction circuit is used as a timing signal for an input waveform shaping circuit in the optical transmitter and a timing output signal of the optical subscriber system bidirectional transmission device. Features.

Means provided by the second invention of the present application to solve the above-mentioned problem includes an optical transmitter that transmits an optical signal to an opposing optical transmission device, and a device that receives an optical signal from the optical transmission device. A timing signal distribution system in an optical subscriber bidirectional transmission device having an optical receiver, the optical transmitter comprising an input waveform shaping circuit and a light emitting element driving circuit that amplifies the output of the input waveform shaping circuit. and a light-emitting element that emits light according to the output of the light-emitting element drive circuit, and the optical receiver includes a light-receiving element, an equalizing amplifier circuit that equalizes and amplifies the output of the light-receiving element, and the equalizer. The optical subscriber system comprises at least a timing signal coarse extraction circuit that extracts a coarse timing signal using an output signal of the amplifier circuit, and an identification and reproduction circuit that identifies and reproduces the output signal of the equalization amplifier circuit. The bidirectional transmission device includes a PLL circuit driven using the coarse timing signal extracted by the rough timing signal extraction circuit, and converts the timing signal output from the PLL circuit into a timing signal for the input waveform shaping circuit. and a timing signal for the identification reproducing circuit and a timing output signal of the optical subscriber system bidirectional transmission device.

[0024]

In the first aspect of the present invention, a timing signal extracted using a timing extraction circuit in an optical receiver is supplied to an optical transmitter as a timing signal for input waveform shaping. As a result, the input waveform shaping circuit in the optical transmitter performs waveform shaping using a timing signal with less jitter and high-frequency noise, so it is possible to generate a data signal with less jitter. Therefore, it is possible to prevent the quality of transmitted data, audio, images, etc. from deteriorating.

In the second aspect of the invention, a stable timing signal output from the PLL circuit is supplied to the optical transmitter as an input waveform shaping timing signal. As a result, in the input waveform shaping circuit in the optical transmitter, the PL
Since waveform shaping is performed using a stable timing signal free of jitter and high frequency noise output from the L circuit, a data signal free of jitter can be generated. Therefore, it is possible to prevent the quality of transmitted data, audio, images, etc. from deteriorating.

[0026]

Embodiment FIG. 1 shows an embodiment in which the timing signal distribution system of the first invention is applied to a bidirectional optical transmission device between a remote multiplexer 9 and a subscriber premises equipment 10 in FIG. It is a block diagram. Here, the optical receiver 1 and optical transmitter 2 in FIG. 1 are generally constructed as shown in FIGS. 5 and 6.

In FIG. 1, the data signal DATA1 (600 Mbps) output from the optical receiver 1 and the timing signal CLK1 (600 Mbps) extracted by the timing extraction circuit and synchronized with the transmission speed are transmitted to the optical subscriber system bidirectional transmission device 5. The timing signal CLK1 is output to the terminal interface device 3 connected to the optical transmitter 2.
It is also supplied as a timing signal for input waveform shaping. In the terminal interface device 3, the input data signal DATA1 and timing signal CLK1 are converted into signals suitable for the signal speed in the terminal device 4 (for example, 150 Mb).
ps) and output to the terminal device 4. In addition, a low-speed data signal (150 Mb) output from the terminal device 4 is also used.
ps) is subjected to signal processing in the terminal interface device 3, outputted as a data signal DATA2 (600 Mbps), and inputted to the optical transmitter 2.

That is, in the configuration of FIG. 1, the optical transmitter 2
The data signal supplied to the terminal interface device 3 is the data signal DATA2 output from the terminal interface device 3, but the timing signal is the timing signal CLK1 extracted by the optical receiver 1, unlike the conventional case shown in FIG.

As a result, the characteristics of the waveform shaping timing signal CLK1 input to the optical transmitter 2 are not affected by jitter generation factors within the terminal interface device 3, and are determined by the timing extraction characteristics of the optical receiver 1. Almost decided. That is, the optical transmitter 2 can be supplied with the waveform shaping timing signal CLK1, which has less jitter than the conventional one and is not affected by high frequency noise caused by signal processing in the multiplexing/separating circuit or the like.

Accordingly, in the timing signal distribution system using the first invention shown in FIG. It becomes possible to generate a data signal with less data. This makes it possible to prevent the quality of transmitted data, audio, images, etc. from deteriorating.

FIG. 2 shows an embodiment in which the timing signal distribution system of the second invention is applied to a bidirectional optical transmission device between the remote multiplexer 9 and the subscriber premises equipment 10 in FIG. It is something.

The optical transmitter 2 in FIG. 2 is generally constructed as shown in FIG. 6. On the other hand, the optical receiver 1 has a configuration as shown in FIG. 3, and the timing signal input to the identification/regeneration circuit 17 is different from that of the optical receiver shown in FIG. In other words, in FIG. 3, the output timing signal CLK1 (600 Mbps) of the timing signal coarse extraction circuit 16', which performs rough timing extraction using the output signal of the equalization amplifier circuit 15, is sent to the identification reproducing circuit 17 using the PLL circuit 6 (FIG. )
Timing signal CLK1 obtained by inputting
1 (600 Mbps) is supplied. Identification reproduction circuit 17
Then, the waveform of the output signal of the equalization amplifier circuit 15 is identified using this CLK11, and the input optical data signal is reproduced as a data signal DATA1 (600 Mbps).

In FIG. 2, a timing signal CLK11 generated by this PLL circuit 6 and synchronized with the transmission speed.
The data signal DATA1 is output to the terminal interface device 3 connected to the optical subscriber system bidirectional optical transmission device 5, and the timing signal CLK11 is also supplied to the optical transmitter 2 as a timing signal for input waveform shaping. . Here, the timing tank in the timing signal rough extraction circuit 16' may be any tank that can roughly extract basic timing components from the data signal. In the terminal interface device 3, the input data signal DATA1 and timing signal CLK11 are converted into a data signal (for example, 150 Mbps) suitable for the signal speed in the terminal device 4, and output to the terminal device 4.

Furthermore, the low-speed data signal (150 Mbps) output from the terminal device 4 is processed by the terminal interface device 3, and the data signal DATA2 (60 Mbps) is processed by the terminal interface device 3.
0 Mbps) and input to the optical transmitter 2.

That is, in the configuration of FIG. 2, the data signal supplied to the optical transmitter 2 is transmitted to the terminal interface device 3.
However, unlike the conventional case shown in FIG. 3, the timing signal is the timing signal CLK11 generated by the PLL circuit 6.

As a result, the characteristics of the waveform shaping timing signal CLK11 input to the optical transmitter 2 are not affected by jitter generation factors within the terminal interface device 3, and are almost determined by the operating characteristics of the PLL circuit 6. be done. That is, the optical transmitter 2 can be supplied with the waveform shaping timing signal CLK11, which has no timing jitter and is not affected by high frequency noise due to signal processing in a multiplexing/separating circuit or the like, unlike the conventional one.

Furthermore, in general, a PLL circuit has the characteristic of following and synchronizing with the frequency fluctuation of an input signal. Therefore, in the timing signal distribution method of the second invention shown in FIG. 2, the speed of the optical data signal input to the optical receiver 1 changes, and the frequency fluctuation occurs in the timing signal CLK1 extracted by the timing signal rough extraction circuit. Even if P
Since the LL circuit 6 follows and synchronizes with the frequency fluctuation, it becomes possible to stably output the timing signal CLK11 without jitter.

Therefore, in the timing signal distribution method using the second invention shown in FIG. 2, the jitter is eliminated by shaping the waveform of the data signal DATA2 using the timing signal CLK11 which has no jitter and does not contain high frequency noise. It becomes possible to generate a data signal without any Also,
Even if the transmission speed of the optical data signal input to the optical receiver 1 changes, the PLL circuit 6 can synchronize by following the frequency fluctuation and stably supply the timing signal CLK11 to the optical transmitter circuit 2. It becomes possible. This results in
It is possible to prevent the quality of transmitted data, audio, images, etc. from deteriorating, and it is also possible to flexibly respond to changes in transmission path speed and frequency fluctuations.

[0039]

As described above, according to the first aspect of the present invention, a timing signal with little jitter and no high frequency noise can be supplied to an optical transmitter as a timing signal for waveform shaping. By shaping the waveform of a data signal using the following method, it is possible to generate a data signal with less jitter and prevent the quality of transmitted data, audio, images, etc. from deteriorating.

According to the second aspect of the present invention, a timing signal without jitter and containing no high frequency noise can be supplied to an optical transmitter as a timing signal for waveform shaping, and this timing signal can be used to adjust the waveform of a data signal. By performing shaping, it becomes possible to generate a data signal without jitter. Furthermore, when the second aspect of the present invention is used, even if the transmission speed of the optical data signal input to the optical receiver changes, the PLL circuit follows the frequency fluctuation and synchronizes, so that jitter is eliminated. It is possible to supply a stable waveform shaping timing signal to the optical transmitter. This makes it possible to prevent deterioration in the quality of transmitted data, audio, images, etc., and also to flexibly respond to changes in transmission path speed and frequency fluctuations.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the first invention.

FIG. 2 is a diagram showing an embodiment of the second invention.

FIG. 3 is a diagram showing an example of the configuration of an optical receiver.

FIG. 4 is a diagram showing an example of a conventional timing signal distribution method.

FIG. 5 is a diagram showing another example of the configuration of an optical receiver.

FIG. 6 is a diagram showing an example of the configuration of an optical receiver.

FIG. 7 is a diagram showing an example of the configuration of an optical subscriber system.

FIG. 8 is a diagram showing an example of a spectrum of an input timing signal of a multiplexing/separating circuit.

FIG. 9 is a diagram showing an example of a spectrum of an output timing signal of a multiplexing/separating circuit.

[Explanation of symbols]

1 Optical receiver 2 Optical transmitter 3 Terminal interface device 4
Terminal device 5 Optical subscriber system bidirectional transmission device 6
PLL circuit 7 Central station 8 CATV center 9 Remote multiplexer 10 Subscriber premises equipment 11 Switch circuit 12 Multiplexing/separating circuit 13 Optical/electrical/electrical/optical conversion circuit 14
Light receiving element 15 Equalization amplifier circuit 16 Timing signal extraction circuit 16' Timing signal rough extraction circuit 17 Discrimination reproducing circuit 18 Input waveform shaping circuit 19 Light emitting element driving circuit 20 Light emitting elements DATA1, DATA2 Data signal CLK1,
CLK11, CLK2 timing signal f0
Basic timing signal frequency 2f0 2nd harmonic frequency

Claims (2)

[Claims] 1. A timing signal in an optical subscriber system bidirectional transmission device having an optical transmitter that transmits an optical signal to an opposing optical transmission device, and an optical receiver that receives the optical signal from the optical transmission device. In the distribution method, the optical transmitter includes:
The optical receiver includes at least an input waveform shaping circuit, a light emitting element drive circuit that amplifies the output of the input waveform shaping circuit, and a light emitting element that emits light in accordance with the output of the light emitting element drive circuit, and the optical receiver includes a light receiving element and a light receiving element. , an equalization amplifier circuit that equalizes and amplifies the output of this light receiving element, a timing signal extraction circuit that extracts a timing signal from the output of this equalization amplifier circuit, and a timing signal output from this timing signal extraction circuit. and an identification/regeneration circuit for identifying and reproducing the output signal of the equalization amplifier circuit, and transmits the timing signal extracted in the timing signal extraction circuit to the timing signal for the input waveform shaping circuit and the optical subscriber. A timing signal distribution method characterized in that the timing signal is used as a timing output signal of a system bidirectional transmission device. 2. A timing signal in an optical subscriber system bidirectional transmission device having an optical transmitter that transmits an optical signal to an opposing optical transmission device, and an optical receiver that receives the optical signal from the optical transmission device. In the distribution method, the optical transmitter includes:
The optical receiver includes at least an input waveform shaping circuit, a light emitting element drive circuit that amplifies the output of the input waveform shaping circuit, and a light emitting element that emits light in accordance with the output of the light emitting element drive circuit, and the optical receiver includes a light receiving element and a light receiving element. , an equalization amplifier circuit that equalizes and amplifies the output of the light receiving element, a timing signal coarse extraction circuit that extracts a coarse timing signal using the output signal of the equalization amplifier circuit, and an output signal of the equalization amplifier circuit. The optical subscriber system bidirectional transmission device further includes a PLL circuit driven using the coarse timing signal extracted by the coarse timing signal extraction circuit. , the timing signal output from the PLL circuit is used as the timing signal for the input waveform shaping circuit, the timing signal for the identification regeneration circuit, and the timing output signal of the optical subscriber system bidirectional transmission device. Signal distribution method.