JPH06104840A - Direct optical amplifier - Google Patents

Abstract

PURPOSE:To transfer alarm information to a down-stream side by superimposing the alarm information onto a stimulated light source as soon as interruption of an input signal light is detected and a standby light source is selected. CONSTITUTION:When an input optical signal is interrupted, a light receiving element 3 and an input interruption detection circuit 4 detect the input interruption and input interruption information from the input interruption detection circuit 4 is inputted to a frequency modulation circuit 8 and a changeover circuit 7. Upon the receipt of the input interrupt information, the frequency modulation circuit 8 generates a digital code pattern in response to the alarm information including a specific number of each optical direct amplifier and converts it into an FSK signal. Furthermore, the FSK signal is inputted to a stimulation semiconductor laser drive circuit 9, which applies light intensity modulation to a stimulation semiconductor laser 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical direct amplifier using a rare earth (Er) -doped fiber, and more particularly to an optical direct amplifier having an optical repeating function.

[0002]

2. Description of the Related Art Conventional optical direct amplifiers include, for example, the document "Optical Fiber Amplifier" Yasuo Kimura, Masataka Nakazawa, OPTRO.
NICS (1990) No. 11, pp. 47-53, which is composed of a pumping semiconductor laser, an optical coupler, a non-polarization type optical isolator, an Er-doped fiber, and an optical bandpass filter.

For the excitation light source, a wavelength of 1.48 μm is InGa
AsP, 0.98 μm is strained superlattice InGaAs, 0.8
A semiconductor laser whose μm is GaAlAs is used. An optical fiber coupler or a dielectric multilayer film mirror is used to combine the signal light and the excitation light. Optical fiber type isolators are inserted at both ends of the Er optical fiber to suppress laser oscillation due to return light. In order to make the best use of the characteristic that the gain of the Er fiber does not depend on the plane of polarization, the optical fiber type isolator uses a non-polarization type for direct optical amplification.

[0004]

In this conventional optical direct amplifier, the main signal light is output from the amplifier when the disconnection of the input signal is detected in the case where the signal light is repeatedly relayed in the transmission line. Consequently, there is no main signal on the downstream side, and the optical communication device located on the most downstream side of this transmission line cannot specify the abnormality occurrence point because the signal light does not arrive.

[0005]

An optical direct amplifier according to the present invention comprises a first optical coupler for branching an input signal light, one signal light branched by the first coupler, and a spare semiconductor laser. Second optical coupler for multiplexing the output light of the above, the EDF of the erbium-doped fiber for directly amplifying the light by inputting the output of the second optical coupler, the signal light of this EDF and the output of the pumping semiconductor laser A wavelength division multiplexing optical coupler for demultiplexing light, a light receiving element for receiving the other signal light branched by the first optical coupler and converting it into an electric signal, and a signal light for receiving the electric signal An input disconnection detection circuit that detects the presence or absence of a signal and outputs it as input disconnection information; a frequency modulation circuit that converts a digital code pattern generated corresponding to the input disconnection information into two FSK modulated signals of different frequencies; Disconnect information Switch circuit for switching to the spare semiconductor laser by force, a drive circuit for the spare semiconductor laser that operates by the output signal of this switch circuit, a spare semiconductor laser having the same wavelength as the signal light, and a pumping light for pumping light with the FSK modulation signal. And a driving circuit for a pumping semiconductor laser that modulates the intensity, and when the signal light is disconnected, transmits the FSK-modulated input disconnection alarm information at a frequency set to a value lower than the low cutoff frequency of the EDF. And means for transferring to the downstream side of the road.

[0006]

The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention.

In this embodiment, a first optical coupler 1 for branching a signal light input from an input terminal, one signal light branched by the first coupler 1 and an output light of a spare semiconductor laser 5 are provided. A second optical coupler 2 for multiplexing the signals, an EDF 11 of an erbium-doped fiber for directly amplifying the light by inputting the output of the second optical coupler 2, a signal light of the EDF 11 and an output light of the pumping semiconductor laser 10. A wavelength division multiplexing third optical coupler for demultiplexing, a light receiving element 3 for inputting the other signal light branched by the first optical coupler 1 and converting it into an electric signal, and an electric signal for inputting the signal light An input disconnection detection circuit 4 for detecting the presence or absence of the input signal and outputting it as input disconnection information; a frequency modulation circuit 8 for converting a digital code pattern generated corresponding to the input disconnection information into two FSK modulated signals having different frequencies; Enter the disconnection information A switching circuit 7 for switching to the semiconductor laser 5, a drive circuit 6 for a spare semiconductor laser that operates with the output signal of the switching circuit 7, a spare semiconductor laser 5 having the same wavelength as the signal light, and an intensity of pumping light with an FSK modulation signal. And a driving circuit 9 for a pumping semiconductor laser that modulates the signal, and warning information of the input interruption, which is FSK-modulated at a frequency set to a value lower than the low cutoff frequency of the EDF 11 when the signal light is disconnected, on the downstream side of the transmission line. Configured to transfer to.

Next, the operation of this embodiment will be described. When an abnormality occurs in the optical fiber transmission line and the optical signal is not input in the optical direct amplifier, the input disconnection is detected by the light receiving element 3 and the input disconnection detection circuit 4. The output of the input disconnection detection circuit is frequency-modulated. It is input to the circuit 8 (FSKCONV) and the switching circuit. In the FSK CONV8, when input disconnection information is input, a digital code pattern corresponding to alarm information including a unique number of each optical direct amplifier is generated, and the digital code pattern is converted into an FSK signal. Further, the FSK signal is transmitted to the driving circuit 9 (L
DD), and the light intensity of the excitation semiconductor laser 10 is modulated.

On the other hand, the spare semiconductor laser drive circuit 6 is controlled by the switching circuit 7 so as to operate, and the spare semiconductor laser 5 is driven by direct current. The wavelength of the spare semiconductor laser is the same as the wavelength of the signal light. The output light of the preliminary semiconductor laser 5 is input to the erbium-doped fiber 11 through the second optical coupler 2, is directly amplified by the light, and is output to the transmission line. In this way, by detecting the disconnection of the input signal light and switching to the auxiliary light source, at the same time, by mounting the alarm information on the excitation light source, the alarm can be transferred to the downstream side.

Further, when the signal light is normally input, the spare semiconductor laser 10 is not driven and the FSK CON
V8 does not operate, and the excitation semiconductor laser 10 operates by direct current emission.

FIG. 2 shows an example of a waveform obtained by FSK-modulating the digital code pattern of this embodiment. Frequency f ₁ for digital code pattern “1” and f for “0”
₀ corresponds. At this time, f ₁ and f ₀ are set within the amplification response band of the optical direct amplifier.

[0012]

As described above, according to the present invention, when the input disconnection is detected, the standby semiconductor laser is switched to, and at the same time, the pumping semiconductor laser is FSK-modulated by the alarm information including the unique number of each optical direct amplifier. As a result, an input disconnection alarm can be transferred to the downstream side, and an abnormal place can be specified.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an example of output light intensity with respect to excitation light intensity of the present embodiment.

[Explanation of symbols]

 1, 2 and 12 Optical coupler 3 Light receiving element 4 Input disconnection detection circuit 5 Spare semiconductor laser 6 Spare semiconductor laser drive circuit 7 Switching circuit 8 Frequency modulation circuit (FSK CONV) 9 Excitation semiconductor laser drive circuit 10 Excitation semiconductor laser 11 Erbium-doped fiber (EDF)

Claims (1)

[Claims] 1. A first optical coupler for splitting an input signal light, and a second light for multiplexing one of the signal light split by the first coupler and an output light of a spare semiconductor laser. A coupler, an EDF of an erbium-doped fiber for directly amplifying the light by inputting the output of the second optical coupler, and a wavelength division multiplexing optical coupler for demultiplexing the signal light of this EDF and the output light of the pumping semiconductor laser. A light receiving element for receiving the other signal light branched by the first optical coupler and converting it into an electric signal; and an input for inputting the electric signal to detect the presence or absence of the signal light and output it as input disconnection information. A disconnection detection circuit, a frequency modulation circuit for converting a digital code pattern generated corresponding to the input disconnection information into two FSK modulated signals having different frequencies, and switching for inputting the input disconnection information and switching to a spare semiconductor laser. A circuit, a drive circuit for a spare semiconductor laser that operates with the output signal of the switching circuit, a spare semiconductor laser having the same wavelength as the signal light, and a pumping semiconductor laser that modulates the intensity of pumping light with the FSK modulation signal. A drive circuit, wherein the EDF is provided when the signal light is disconnected.
FS at a frequency lower than the low cutoff frequency of
An optical direct amplifier, comprising means for transferring K-modulated alarm information of an input break to a downstream side of a transmission line.