JPH07114386B2 - Optical transmission system - Google Patents

Description

The present invention relates to means for transmitting a supervisory control signal of a repeater used in an optical cable communication system.

〔Overview〕

According to the present invention, a means for transmitting a phase change of a phase corresponding to a supervisory control signal to a phase of a main optical signal, and transmitting the supervisory control signal, the phase of light passing through an optical transmission line is changed according to a change of an emission wavelength. It is possible to prevent the deterioration of the S / N ratio of the transmitted supervisory control signal even in the case of multiple relays by utilizing the phenomenon that occurs.

[Conventional technology]

As a conventional technique for transmitting the supervisory control signal of the repeater,
There is a phase modulation method using a low frequency of a transmission signal. In this method, the clock component included in the transmission signal is e (t) =
cos (ω ₀ t + ΔΦ cospt) (where e (t) is the standardized clock signal, ω ₀ is the standard angular frequency, ΔΦ is the magnitude of the phase angle, p is the angular frequency for phase modulation, and t is the time. .) Is transmitted to transmit the supervisory control signal.

[Problems to be solved by the invention]

Since such a conventional phase modulation method is direct transmission through a repeater, there are restrictions depending on the circuit characteristics (generally, the characteristics of the filter because a filter is used) for extracting the clock component from the transmission signal. receive.

That is, the phase modulation frequency is the clock frequency f ₀ of the main signal.
The attenuation must be within a flat bandwidth due to the filter characteristics in the vicinity, and during multi-relay, jitter accumulates in the above-mentioned band and the S / N ratio of the supervisory control signal due to phase modulation deteriorates. There is.

The present invention eliminates such drawbacks, and an object of the present invention is to provide an optical transmission system capable of preventing deterioration of the S / N ratio of a supervisory control signal due to phase modulation even in multiple repeaters.

[Means for solving problems]

According to the present invention, a main optical signal that is inserted into an optical transmission line and arrives at this transmission line is relayed and reproduced into a main optical signal of a predetermined level, and a relay unit having a light emitting unit and a phase of a reference clock of the main optical signal In an optical repeater comprising a detection means for detecting a time change and a monitor control means for making a predetermined monitor control code correspond to the time change of the phase detected by this means, the light emitting means has an emission wavelength of It emits controllable coherent light, and is characterized by including an emission wavelength control means for modulating the emission wavelength of the emission means in accordance with a supervisory control code.

[Action]

The supervisory control signal of the repeater is transmitted corresponding to the time change of the phase of the main optical signal. By the way, an optical signal passing through the optical fiber has a wavelength delay difference due to the dispersion effect of the optical fiber, and this delay amount corresponds to the frequency of the wavelength of the optical signal. The present invention utilizes this principle to give a time change in phase as an optical wavelength modulation frequency to an optical signal to transmit information to a next repeater.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment system of the present invention. The signal received by the APD module 5 is delivered to the identification reproduction unit 1, and the signal branched from the identification reproduction unit 1 is transmitted to the phase detection reproduction circuit 2. The phase detection / reproduction circuit 2 detects and reproduces the phase change of the transmission signal included in the received signal, and the reproduced signal optically converts the outputs of the supervisory control circuit 4 for performing supervisory control of the repeater and the identification reconstruction unit 1. Is transmitted to the laser module 3 having the emission wavelength control function, and the emission wavelength of the laser module 3 is controlled and modulated. When a signal whose emission wavelength is modulated by the repeater 7 passes through the optical fiber 6, a wavelength delay difference occurs due to dispersion of the optical fiber. When the transmission signal is received and amplified by the APD module 5 of the repeater 8, the phase of the transmission signal fluctuates from the waveform of the solid line to the waveform of the broken line according to the modulation frequency of the emission wavelength as shown in FIG. This phase change is detected and regenerated by the phase detection / regeneration circuit 2 of the repeater 8, the emission wavelength of the laser module 3 is modulated again, and information is transmitted to the next repeater.

Next, the operation of the repeater will be described with reference to FIG. The transmission signal passing through the optical fiber 6 and detected by the APD module 5 is amplified by the amplifier circuit 11 to a specified level, and the output of the amplifier circuit 11 is the identification circuit 12 and the timing recovery circuit 13
And the phase detection / reproduction circuit 2. Since the phase of the received signal fluctuates as shown in FIG. 3, this information is reproduced by the phase detection / reproduction circuit 2 as the phase change frequency. On the other hand, the timing reconstruction circuit 13 generally uses a filter having a high tank rate in order to stably detect the timing component from the received signal. Therefore, the fluctuation of the phase of the main reception signal is suppressed by this filter characteristic. Further, since the identification circuit 12 reproduces the transmission signal in synchronization with the signal reproduced by the timing reproduction circuit 13, the output of the identification circuit 12 becomes a signal having only the frequency component of the transmission signal without phase change, It is transmitted to the laser module drive circuit 14. Laser module 3 with emission wavelength control function
Optically converts the transmission signal based on the output of the laser module drive circuit 14. The output of the phase detection / reproduction circuit 2 is connected to the laser module 3 and controls the emission wavelength of the laser module 3. Further, the phase change information is also connected to the supervisory control circuit 4, and the phase change information is decoded by the supervisory control circuit 4 as a control signal code determined according to the frequency of the phase change or the presence or absence of phase modulation, and the supervisory control of the repeater. It performs various operations related to.

〔The invention's effect〕

As described above, the present invention converts a supervisory control signal into a change in emission wavelength and transmits it, and after passing through an optical fiber, it appears as phase modulation, which is detected by a repeater and detected in a change in emission wavelength. Since it is converted again and transmitted, there is an effect that the deterioration of the S / N ratio in the transmission line of the supervisory control signal can be suppressed. Further, an arbitrary frequency outside the band of the filter can be selected by the clock component extraction circuit, and even if the Q of the filter is increased to suppress the jitter, the transmission of the supervisory control signal is not affected. There is an effect that the S / N ratio of the main signal system can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of the repeater shown in FIG. FIG. 3 is a waveform diagram showing changes in the waveform of the transmission signal. 1 ... Identification reconstruction unit, 2 ... Phase detection / regeneration circuit, 3 ... Laser module, 4 ... Monitoring control circuit, 5 ... APD module, 6 ... Optical fiber, 7, 8 ... Repeater, 11 ......
Amplification circuit, 12 …… Identification circuit, 13 …… Timing recovery circuit, 14 …… Laser module drive circuit.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H04J 14/04 14/06

Claims (1)

[Claims] Claim: What is claimed is: 1. A main optical signal which is inserted into an optical transmission line and arrives at the transmission line is relayed and reproduced into a main optical signal of a predetermined level, and a relay unit having a light emitting unit and a phase of a reference clock of the main optical signal. In the optical repeater, the light emitting means includes a detecting means for detecting a time change of the light source and a monitor control means for making a predetermined monitor control code correspond to the time change of the phase detected by the means. The optical transmission system is characterized in that it emits coherent light that can be controlled by a light emitting wavelength control means for modulating the light emitting wavelength of the light emitting means according to a supervisory control code.