JP3104426B2 - Optical communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication apparatus, and more particularly to an optical communication apparatus for adding a channel identification signal in special coherent FDM.

[0002]

2. Description of the Related Art In a conventional optical communication apparatus, a coherent FDM channel identification circuit includes, as shown in FIG. 2, a transmission source (1) and a transmission source (n) 2 and an oscillator (1) transmitting at different frequencies. ) 5 to transmitter (n) 6 and each transmission source 1
2 and adders (1) 3 to (n) 4 for adding the oscillators 5 and 6, and a laser diode (1) 7 which oscillates at an equal interval spectrum using the output of each adder 3 and 4 as a modulation signal.
~ LD (n) 8 of laser diode and LD7,8
Comprising a multiplexed optical coupler 9 for frequency-multiplexing the output of
A channel frequency multiplexing transmitter, an optical receiving unit 11 for converting a station output from the wavelength tunable station issuing unit 10 and an optical input signal into an electric signal, and an amplifier 1 for amplifying an output of the optical receiving unit 11
2, a frequency discriminator 14 for obtaining frequency information from the output of the frequency discriminator 2, a low-pass filter 16 for extracting a channel identification signal from the output of the frequency discriminator 14, and a channel discrimination signal read from the output of the low-pass filter 16 as a local light. And a channel identification receiver having a control unit 18 that feeds back to the channel identification receiver.

Next, the operation of the conventional example will be described.

The channel identification signals of the n-channel frequency multiplexing transmitter are output signals of oscillators (1) 5 to (n) 6 oscillating at different frequencies, and transmission sources 1 and 2 and each channel identification signal are added. Unit (1) 3 to adder (n)
Add 4 L at the transmission source to which the channel identification signal is added
D is modulated and frequency-multiplexed by the multiplexing optical coupler 9.

In a channel identification receiver, an optical receiving unit 11
Then, the light from the wavelength tunable local light emitter 10 is multiplied by an optical input signal to convert it into an electric signal. The output of the optical receiver 11 is amplified by the amplifier 12, searched by the detector 13, and outputs a signal 23.

On the other hand, frequency information is obtained from the output of the amplifier 11 from the frequency discriminator 14 and a channel identification signal is extracted from the output of the frequency discriminator 14 by the low-pass filter 16. The control unit 18 determines whether the currently requested channel is the same as the channel identification signal output from the low-pass filter 16. If they are different, the wavelength tunable local oscillator 10 is locked to the adjacent channel, and the channel is identified again.

[0007]

In this conventional optical communication apparatus, the coherent FDM channel identification signal modulates the transmission light source itself with the channel identification signal, so that the spectral line width becomes large and the receiving sensitivity of the receiver becomes large. There is a problem in that it directly affects the degradation and makes it impossible to make use of the improvement in the receiving sensitivity, which is the greatest advantage of coherent optical communication.

[0008]

An optical communication apparatus according to the present invention comprises:
A plurality of oscillators each for oscillating a different frequency for channel identification corresponding to a plurality of input transmission sources; a plurality of adders for respectively adding signals from the respective transmission sources and the respective oscillators; A multiplexed optical coupler that multiplexes and transmits optical signals at equal intervals based on signals from a device, and discriminates a channel identification signal by an electrical signal from a light obtained by combining the light from the wavelength tunable local oscillator and the received optical signal. Having a frequency discriminator and a low-pass filter, and a control unit, wherein the control unit controls the wavelength of the wavelength-variable local oscillator until the required channel matches the channel identification signal, when a being requested channel and the channel identification signal matches, the channel identification signal and the frequency output from the frequency variable oscillator, to modulate said wavelength tunable station emitter with signals having the same phase It allows, characterized in that to prevent deterioration of receiving sensitivity.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of one embodiment of the present invention.

In this embodiment, a plurality of input transmission sources 1,
A plurality of oscillators 5 and 6 each of which oscillates a different frequency for identifying a channel corresponding to 2 and a plurality of adders 3 and 4 which respectively add signals from the transmission sources 1 and 2 and the oscillators 5 and 6 respectively. A plurality of laser diodes 7 and 8 that emit light at equal intervals according to the signals from the adders 3 and 4 and output optical signals; a multiplex optical coupler 9 that multiplexes and transmits a plurality of optical signals; An optical receiver 11 for converting and outputting light obtained by combining light from the variable local oscillator 10 and a received optical signal into an electric signal, a frequency discriminator 14 for discriminating a channel identification signal by the electric signal, and a low-pass filter The controller 16 outputs the frequency of the channel identification signal when the requested channel and the channel identification signal match, and outputs the frequency of the adjacent channel when the channel identification signal does not match and controls the wavelength tunable local oscillator 10. Part 18 Configured to have a.

Next, the operation of this embodiment will be described.

The channel identification signals of the n-channel frequency division multiplexing transmitter are output signals of oscillators (1) to (n) 6 transmitting at different frequencies, and transmission sources 1 and 2 and each channel identification signal are added. Unit (1) 3 to adder (n)
Add 4 The laser diodes (LD) 7 and 8 are modulated by the transmission source to which the channel identification signal is added, and frequency-multiplexed by the multiplex optical coupler 9.

In the channel identification receiver, the optical receiver 11
Then, the light from the wavelength tunable local light emitter 10 is converted into an electric signal by applying an optical input signal. The output of the optical receiving unit 11 is
The signal is amplified by 2 and detected by the detector 13 to output a signal 23.

On the other hand, frequency information is obtained from the output of the amplifier 12 from the frequency discriminator 14, and a channel identification signal is extracted from the output of the frequency discriminator 14 by the low-pass filter 16. The control unit 18 determines whether the currently requested channel is the same as the channel identification signal output from the low-pass filter 16. If the channel is the same as the requested channel, the control unit 18 controls the variable frequency oscillator 20 to oscillate at the same frequency and the same phase as the channel identification signal.
Is switched to the variable frequency oscillator 20, and the local light is modulated by the output of the variable frequency oscillator 20. If not, the switch 22 is switched to the control unit 18, the wavelength tunable local oscillator 10 is locked to an adjacent channel, and channel identification is performed again.

[0015]

As described above, according to the present invention, the local line light is also modulated at the same frequency and the same phase as the channel identification signal that modulates the transmission light source itself after the channel identification. This has the effect that the thickness does not increase and the reception sensitivity does not deteriorate.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of an example of a conventional optical communication device.

[Explanation of symbols]

 Reference Signs List 1 transmission source (1) 2 transmission source (n) 3 adder (1) 4 adder (n) 5 oscillator (1) 6 oscillator (n) 7 laser diode (1) 8 laser diode (n) 9 multiplex optical coupler REFERENCE SIGNS LIST 10 wavelength variable local light emitter 11 optical receiving unit 12 amplifier 13 detector 14 frequency discriminator 16 low-pass filter 18 control unit 20 frequency variable transmitter 21 adder 22 switch 22 received signal

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁷ Identification code FI H04J 14/02

Claims (1)

(57) [Claims] 1. A plurality of oscillators each oscillating a different frequency for channel identification corresponding to a plurality of input transmission sources, and a plurality of adders for adding signals from the transmission sources and the oscillators, respectively. A multiplexed optical coupler for multiplexing and transmitting optical signals at equal intervals by the signals from the adders, and a light obtained by combining the light from the wavelength tunable local oscillator and the received optical signal with an electric signal. A frequency discriminator and a low-pass filter for discriminating a channel identification signal, and a control unit, wherein the control unit controls the wavelength tunable local oscillator until the requested channel matches the channel identification signal. Controlling the wavelength, and when the required channel matches the channel identification signal, the wavelength-variable local oscillator is generated by a signal having the same frequency and phase as the channel identification signal output from the frequency variable oscillator. An optical communication device wherein modulation of an optical device prevents deterioration of reception sensitivity.