JPH0661946A - Sv/alc signal superposing method - Google Patents

Abstract

PURPOSE:To provide an SV/ALC signal superposing method in an optical RCM communication system to exclude the frequency component equal to the SV/ALC control signal which monitors and controls a repeater out of a main signal and to improve the S/N. CONSTITUTION:An SV/ALC signal superposing method includes an O/E converter 20 which converts an optical main signal into an electric signal, a BPF 30 which extracts the SV signal frequency component, a BPF 40 which extracts the ALC signal frequency component, an inverter/amplifier 70 which inverts and amplifies the input signal, an adder 80 which adds together the outputs of an SV oscillator 60 and an ALC oscillator 61, and an external modulator 10 which modulates the optical signal with use of the input signal. The frequency component equal to the SV/ALC control signal are extracted out of the main signal via both BPF 30 and 40. Then the signal inverted and amplified by the amplifier 70 is added to the outputs of both oscillators 60 and 61 by the adder 80. Thus a signal is acquired and used to modulate the optical signal to be sent to a repeater through the modulator 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an SV / ALC signal superimposing method for transmitting a control signal for monitoring and controlling an optical PCM communication type repeater in service.

[0002]

2. Description of the Related Art A conventional example will be described with reference to FIG.
FIG. 5 is a diagram showing an example of a conventional SV signal / ALC signal superimposing method.

In an optical PCM terminal device, a supervisory control signal (hereinafter referred to as an SV signal) for monitoring the optical reception level and the optical transmission level of a repeater, forming a loopback circuit, etc.
An optical output level automatic control signal (hereinafter referred to as an ALC signal) for controlling the SV signal f _SV generated by the oscillator 60 and the optical output level automatic control circuit in the repeater so as to keep the amplification degree of the repeater constant. The ALC signal f _ALC generated by the oscillator 61 is added by the adder 81, then added and superposed on the main signal, and the laser diode LD15 is directly modulated by a signal obtained by amplifying all signals by a constant value, and optical modulation is performed. The signal was taken out and sent to the repeater.

[0004]

However, in the conventional SV signal / ALC signal superimposing method, since the main signal is digital PCM data, the S signal is originally S
Since the V signal and the same frequency component as the frequency of the ALC signal are included, there is a problem that the S / N ratio of these control command signals is bad.

The present invention solves the above problem, and it is possible to improve the S / N ratio by removing the frequency components of the SV signal and the ALC control signal included in the main signal.
It is an object to provide a V / ALC signal superimposing method.

[0006]

FIG. 1 is a block diagram showing the principle of an SV / ALC signal superimposing method according to the present invention. In the figure,
The same reference numerals as those in FIG. 5 indicate the same things, 10 is an external modulator,
Reference numeral 20 is an O / E converter, 30 is a bandpass filter (BPF-SV) that passes SV signal frequency components, and 40 is a bandpass filter (BPF-AL) that passes ALC signal frequency components.
C), 60 is an SV signal oscillator, 61 is an ALC signal oscillator, 70 is an inverting amplifier, and 80 is an adder.

According to the present invention, a supervisory control signal 60 for monitoring and controlling an optical repeater in-service from an optical terminal device of an optical PCM communication system, and an optical output level automatic control for controlling output level adjustment of the optical repeater. In the SV / ALC signal superimposing method of superimposing the signal 61 on the main signal and transmitting the same, after demultiplexing an optical signal including the main signal to be transmitted, a supervisory control signal frequency component is output to the output of the O / E converter 20 for converting the optical signal into an electric signal. And a band-pass filter BPF-ALC40 for extracting the frequency component of the optical output level automatic control signal.
An inverting amplifier 70 that inverts and amplifies the polarities of the output signals of the two band-pass filters 30 and 40, the monitoring control signal 60, the optical output level automatic control signal 61, and the output signal of the inverting amplifier 70. And an optical adder for adding a constant modulating voltage to the output signal of the adder 80, and an optical signal including a main signal sent as an output signal from the modulating voltage adder. An external amplifier 10 having an intensity modulation function of intensity-modulating a signal is provided.

Then, the optical signal including the main signal to be transmitted is demultiplexed and converted into an electric signal, and the bandpass filters 30 and 40 are provided.
The supervisory control signal frequency component and the optical output level automatic control signal frequency component extracted via
After inverting and amplifying the signal by adding the monitoring control signal 60 and the optical output level automatic control signal 61 to the output signal of the inverting amplifier 70, the inverting amplifier 70 in the external modulator 10 The object can be achieved by modulating the optical signal to be transmitted with a signal obtained by adding a constant modulation voltage to the voltage signal.

[0009]

In the present invention, the bandpass filter BPF-SV30 is provided at the output of the O / E converter 20 for demultiplexing the optical signal including the main signal to be sent out and then converting it into an electric signal, and the SV signal frequency component is extracted. Further, a bandpass filter BPF-ALC 40 is provided to extract the ALC signal frequency component.

Here, the SV which is the output of the bandpass filter 30.
As means for removing the signal frequency component and the ALC signal frequency component which is the output of the bandpass filter 40, the outputs of the bandpass filters 30 and 40 are inverted and amplified by the inverting amplifier 70.

[0011] Then, by providing the adder 80 adds the the inverted amplified signal, and an output signal f _ALC output signal f _SV and ALC oscillator 61 of the SV oscillator 60. At this time, the output signal of the adder 80 has frequency components as shown in FIG.

The output signal of the adder 80 thus obtained is applied to the external amplifier 10. Then, a predetermined voltage is added so that the signal having the − voltage level is used to obtain a voltage sufficient for modulating the optical signal including the main signal.

By intensity-modulating the optical signal to be transmitted by the signal of the voltage level thus obtained, the SV control signal is generated after removing the SV signal frequency component contained in the main signal, and the ALC signal frequency component is generated. After removing
An LC control signal can be generated.

[0014]

EXAMPLES Examples will be described with reference to FIGS. FIG. 2 is a diagram showing an embodiment of an SV / ALC signal superimposing method according to the present invention, and FIG. 3 is an SV / ALC signal superimposing method for superimposing on a main signal of the present invention.
FIG. 4 is an explanatory diagram (1) of the V signal and the ALC signal, and FIG. 4 is an explanatory diagram (2) of the SV signal and the ALC signal superimposed on the main signal of the present invention.

In the figure, the same reference numerals as those in FIG.
11 is an intensity modulator of the external modulator 10, 12 is a voltage adder for modulation of the external modulator 10, 13 is an optical coupler, 50, 81
Is an adder.

The embodiment of FIG. 2 will be described with reference to FIGS. 3 and 4. The O symbol in FIG. 2 matches the signal component in FIGS. (1) P sent from an optical transmitter (OS) not shown
A part of the CM-encoded optical signal (of FIG. 3) is used as an optical coupler 1.
After branching at 3, the O / E converter 20 converts the electric signal into an electric signal and extracts the main signal. (2) The main signal extracted by the O / E converter 20 is passed through the bandpass filters BPF-SV30 and BPF-ACL40 to extract the frequency components equal to the SV signal and the ALC signal included in the main signal, and further added The SV signal and the ALC signal component are added by using the device 50. (FIG. 3) (3) The output of (2) above is inverted and amplified to a predetermined amount by the inverting amplifier 70 (FIG. 3). (4) SV signal generated by the SV signal oscillator 60 and ALC
The ALC signal generated by the signal oscillator 61 is added using the adder 81. Here, in the case of the SV signal, when it is not necessary to monitor and control, the SV signal is transmitted when the SV control voltage for controlling the stop of the transmission of the SV signal is set to "H", and "L" is output. When set to "", sending is stopped. (5) The output of (3) above and the output of (4) above are added using the adder 80. (FIG. 4) (6) The output of (5) above is applied to the external modulator 10 and converted to a predetermined positive voltage level by the adder 12 in order to obtain a modulation signal necessary for intensity-modulating the optical signal. The intensity modulator 11 (of FIG. 3) intensity modulates the optical signal. (7) As a result, the SV signal frequency component and the ALC signal frequency component are removed, and after the removal, the optical signals in which the SV signal and the ALC signal are generated are output (FIG. 3).
of).

Here, the intensity modulator 11 of the external modulator 10
As an example of the above, a waveguide type modulator configured by a diffusion type waveguide on the surface of LiTaO ₃ or LiNbO ₃ to change the degree of coupling by applying a voltage between two waveguides of a directional coupler Can be used.

The band pass filter BPF-SV30, BP
It is considered that the influence on the main signal by passing through the F-ALC 40 is hardly influenced because the bandwidth of the bandpass filters 30 and 40 is several KHz.

[0019]

As described above, according to the present invention,
Since the same frequency components as the SV signal frequency and the ALC signal frequency included in the main signal are removed in the optical transmission section of the optical PCM terminal device, the main signal is modulated with the SV signal frequency and the ALC signal frequency. As a result, the stability of the repeater operation is improved, and there is the effect of preventing erroneous operation during operation and maintenance.

The present invention can of course be applied to a response signal sent from the repeater to the optical terminal equipment. Further, the present invention has an effect that it can be applied not only to the optical PCM communication system but also to a general wire transmission system and a wireless transmission system.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of an SV / ALC signal superimposing method according to the present invention.

FIG. 2 is an embodiment of an SV / ALC signal superimposing method according to the present invention.

FIG. 3 is a diagram (No. 1) explaining an SV signal and an ALC signal to be superimposed on a main signal of the present invention.

FIG. 4 is a diagram (No. 2) explaining an SV signal and an ALC signal superimposed on a main signal of the present invention.

FIG. 5 is a diagram showing an example of a conventional SV / ALC signal superimposing method.

[Explanation of symbols]

 10 External Modulator 11 Intensity Modulator 12 Modulation Voltage Adder 13 Optical Coupler 14 Intensity Modulator 15 Laser Diode (LD) 20 O / E Converter 30 Bandpass Filter (BPF-SV) 40 Bandpass Filter (BPF-ALC) ) 50, 80, 81, 82 adder 60 monitoring control signal, SV oscillator 61 optical output level automatic control signal, ALC oscillator 70 inverting amplifier 90 amplifier

Claims (1)

[Claims] 1. A monitor control signal (60) for monitoring and controlling an optical repeater in-service from an optical terminal device of an optical PCM communication system, and an optical output level automatic control for controlling output level adjustment of the optical repeater. In an SV / ALC signal superimposing method for superimposing a signal (61) on a main signal and transmitting the superposed signal, the output of an O / E converter (20) for demultiplexing an optical signal including the main signal to be transmitted and converting it into an electric signal is monitored. The band-pass filter BPF-SV (30) for extracting the control signal frequency component, the band-pass filter BPF-ALC (40) for extracting the optical output level automatic control signal frequency component, and the two band-pass filters (30, 40) An inverting amplifier (70) that inverts and amplifies the polarity of the output signal, the monitor control signal (60), the optical output level automatic control signal (61), and the output signal of the inverting amplifier (70) are added. Adder (80), a modulation voltage addition function of adding a constant modulation voltage to the output signal of the adder (80), and an optical signal including a main signal transmitted as an output signal from the modulation voltage addition function. An external amplifier (10) having an intensity modulation function for intensity modulation is provided, and an optical signal including the main signal to be transmitted is demultiplexed and converted into an electrical signal, which is taken out through the bandpass filter (30, 40). The monitoring control signal frequency component and the optical output level automatic control signal frequency component are inverted and amplified by the inverting amplifier (70), and the monitoring control signal (60) and the optical output level automatic control signal ( 61) is added to the output signal of the inverting amplifier (70), and then the external modulator (10) outputs a signal obtained by adding a constant modulation voltage to the negative voltage signal. SV / A characterized by modulating an optical signal C signal superimposing method.