KR960012978B1 - Optical fdm system - Google Patents

Abstract

a wave arranging unit(1) for rearranging a drift, caused by transmission lines and optical devices, using a non degenerate four wave mixing of a semiconductor optical amplifier; a control unit(2) for matching the first. main carrier of a rearranged channel to an optical sync. signal by receiving the wave arranging unit output through a corresponding coupler(5) after dividing it using a splitter(4); a fixed filter unit(3) for outputting channels having an equal interval after separating and extracting those from rearranged channels with a sync. method.

Description

Channel Separation / Extraction Device for Optical FDM System

1 is a block diagram of a channel separation / extraction apparatus according to the present invention.

2 is a diagram illustrating a center frequency arrangement according to the present invention.

The present invention is directed to an optical optical frequency division multiplexing (FDM) system having a function of operating at a frequency interval of about 10 sub-nanometers and having a transmission rate per channel within several tens of Mbps. The present invention relates to a channel separation / extraction apparatus of an optical FDM system capable of separating / extracting incoming channels arranged at equal frequency (optical carrier) intervals in a synchronous manner at a receiver.

Recently, many studies on subscriber optical FDM systems that transmit different types of signals on separate optical carriers and transmit them through a single fiber have been published. Research is underway to narrow down as much as possible. As a method for finely separating and extracting the incoming channels at a narrow interval from the receiver, there may be a method of separating and extracting each channel asynchronously. However, as the number of channels increases due to the redundant use of the control unit for controlling the respective channels, The disadvantage of complex configuration is that the benefits of equally spaced frequency channel allocation are lost. Furthermore, in optical FDM systems, the asynchronous inverse at the receiver is increased due to variations in the transmission channel frequencies caused by the use of different channel allocators per system (e.g., optical resonators) to increase the transmission capacity. Since multiple extraction methods are used and a controller by dithering method must be attached to each filter, the configuration becomes very complicated. When the system is operated by the optical network, this method causes a problem in synchronization. There is this.

The present invention devised to solve the problems of the prior art, the wavelength drift phenomenon between the optical device using the wavelength (or frequency) of each mounting system channel transmitted or the system coming in through different paths to the optical synchronization signal An object of the present invention is to provide a channel separation / extraction apparatus of an optical FDM system that can be separated / extracted in a synchronous manner using an optical filter that is rearranged and fixed at equal intervals in the next stage.

In order to achieve the above object, the present invention, the wavelength alignment means for rearranging and outputting the wavelength drift value due to the transmission path and the optical device using the non-degenerate Four Wave Mixing (SOA); Control means for receiving the output of the wavelength alignment means through a coupler corresponding to each signal as a signal distributed by a splitter and providing the first center carrier of the rearranged channel to the wavelength alignment means in accordance with the received optical synchronization signal; And fixed filter means for outputting channels at equal intervals by separating / extracting the rearranged channels of the wavelength alignment means inputted through the splitter and the coupler in a synchronous manner.

Hereinafter, with reference to the accompanying drawings will be described an embodiment according to the present invention;

1 is a block diagram of a channel separation / extraction apparatus according to the present invention, and FIG. 2 is an exemplary diagram of a center frequency array according to the present invention. In FIG. 1, 1 represents four light mixing effects of a semiconductor optical amplifier (SOA). a wavelength aligner that realigns the drift wavelengths due to the transmission path and the optical device (e.g., optical resonator) using non-degenerate Four Wave Mixing, and 2 is a first center carrier of the rearranged channel according to the received optical synchronization signal. The control unit 3 is a fixed filter unit having equal intervals for separately extracting rearranged channels.

Each block will be described in detail as follows.

The signal of the channel enters f1 (where f1 coincides with the optical synchronizing signal frequency f at the transmitter), f2, f3 in the optical frequency domain, maintaining an equal interval of Δf and setting the wavelength of the channel allocator (e.g., optical resonator). In the case of drift by df due to the wavelength shift caused by the error, the center frequency of each channel is f1 + df, f2 + df, and f3 + df, so that these center frequencies are properly separated / extracted from the next fixed filter unit 3. Can not. Therefore, the wavelength (or frequency fp) of the pumping laser diode (LD) entering the SOA of the wavelength alignment unit 1 is divided by the splitter 4 and set as shown in FIG. 2 to transmit the signal and the optocoupler 5 transmitted from the transmitter. When sent together, it is aligned with the frequency fp of channel 1 by the four-light mixing effect in the SOA. The outputs f1 ', f2', ..., fn 'generated by the four-light mixing effect in the SOA by receiving the signals f1, f2, ..., fn sent from the transmitter are the Guangdong received from the controller 2 The pre-signal wavelength (f in the frequency concept) and another optocoupler 5 are mixed and the differences f3'-f, f2'-f and f1'-f are detected by the photodetector. After the output of the photodetector passes through the low pass filter smaller than the cutoff frequency Δf, an amplitude value corresponding to the value of f1'-f is obtained, and the PID (Proportional Integration Differentia) control unit 2 corresponds to this value. The frequency fp of the pumping LD is adjusted until the applied current of the pumping LD is changed so that the value of f1'-f becomes 0 (f1 '= f). In the fixed filter unit 3, the center pass bands of the optical filters are arranged at intervals of Δf with respect to f so that the control unit 2 synchronously separates / extracts the rearranged channels.

In the mounting systems 1, 2, ..., n having the deviation as shown in FIG. 2, the respective channel 1 frequencies are also synchronized to each of fp in the same manner as described above.

Therefore, the effect of the present invention as described above, by synchronizing the deviation between the channel frequency of each mounting system in accordance with the optical synchronization signal on the receiving side, the channel frequency of each channel multiplexed in the mounting system is then simply separated / fixed as a fixed optical filter. This allows the system to be simplified and to operate in a synchronous network.

Claims (1)

A wavelength alignment means (1) for rearranging and outputting the wavelength drift values caused by the transmission path and the optical element used by using a non-degenerate four wave mixing (SOA) method of the optical optical amplifier (SOA); The wavelength alignment means 1 receives the output of the splitter 4 through the coupler 5 corresponding to each signal as a signal distributed by the splitter 4 so that the first center carrier of the rearranged channel is aligned with the received optical synchronization signal. Control means (2) for providing the means (1); And fixed filter means (3) for outputting channels at equal intervals by separating / extracting the rearranged channels of the wavelength alignment means (1) input through the splitter (4) and the coupler (5) in a synchronous manner. Channel separation / extraction apparatus of an optical F. D. system (FDM) system, characterized in that.