KR20000044269A - Interoffice transmit unit in wavelength division multiplex system - Google Patents

Abstract

PURPOSE: An interoffice transmit unit in a wavelength division multiplex system is provided to increase an expansibility of a system and a network by being capable of interoffice-transmitting a channel signal demultiplexed by a wavelength division, without using an extra repeater. The interoffice transmit unit is provided to detect channel errors demultiplexed by the wavelength division, without an extra counter. CONSTITUTION: In a wavelength division multiplex system which divides optical signals according to each channel, and transmits the divided signals to each determined lower systems, an interoffice transmit unit comprises an optical receiver module(200) and an optical transmitter module. The optical receiver module(200) inputs one channel signal to transmit to a lower system requested for an interoffice transmits and converts into an electronic signal, to extract data. The optical receiver module(200) is composed of an optical detect element(202), a limiting amplifier(204), a clock and data restorer(206). The optical detect element(202) detects an input channel signal optically, to convert into the electronic signal. The limiting amplifier(204) amplifies the converted electronic signal limitedly. The clock and data restorer(206) extracts the data and the clock from an output signal from the limiting amplifier(204). The optical transmitter module is connected to an interoffice optical transmit path which is connected to the lower systems and the optical receiver module(200), and converts the extracted data into an optical signal, to transmit to the lower system.

Description

Channel signal station transmission unit in wavelength division multiplexing system

The present invention relates to a wavelength division multiplexing (WDM) system, and more particularly, to an apparatus for interoffice transmission of a wavelength division demultiplexed channel signal.

The WDM method is one of transmission methods used to transmit an optical signal, and a method of simultaneously guiding a plurality of optical signals having different wavelengths onto one strand of optical fiber. In the WDM method, multiplexing optical signals of different wavelengths into one strand of optical fiber is called wavelength division multiplexing, and conversely, separating optical signals multiplexed into one strand of optical fiber is called wavelength division demultiplexing.

This WDM transmission technology is the easiest way to increase the transmission capacity in an optical communication network, and the WDM system is an embodiment of this. The WDM system transmits the data of multiple channels by wavelength division multiplexing, while the received data is wavelength division demultiplexed to distribute the data to the lower system. At this time, the transmitting side allocates a signal transmitted from a lower system having an arbitrary wavelength to a predetermined specific wavelength and multiplexes it to 20/40/80 Gbps or more ultra-high speed signal. After that, the optical signal transmitted through the optical amplifier and the optical fiber transmission path of the multiple stages separates the channels by the wavelength division demultiplexer at the receiving side and transmits the separated channel signals to the predetermined subsystem. The wavelength division multiplexing wavelength is defined as a standard in the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T). Wavelength division multiplexing is implemented using an optocoupler or an arrayed waveguide grating (AWG), and wavelength division demultiplexing is implemented using an AWG or fiber bragg grating (FBG). As the optical amplifier, EDFA (Erbium-Doped Fiber Amplifier) is used. Sub-systems also become low-speed transmission equipment, for example 2.5Gbps Synchronous Digital Hierarchy (SDH) equipment.

As described above, the channel signal separated by the wavelength division demultiplexer at the reception side is directly transmitted to the sub system without an additional device. The block diagram of the conventional WDM system receiving side is shown in FIG. In FIG. 1, the wavelength division demultiplexer 100 demultiplexes a WDM optical signal received through the WDM optical transmission path 102 to separate optical signals for each channel, and separates the separated channel signals into sub-systems S1 to Sn. Send to each specified subsystem. In the example of FIG. 1, there are n channels.

On the other hand, in the above structure, since the optical output of the demultiplexed channel signal is different for each channel and the intensity of the output itself is not large, only internal transmission is possible. That is, the gain characteristics of the EDFA are different for each channel, and the output of the wavelength division demultiplexer 100 is different while passing through several EDFAs, and the intensity of the output is not large enough to transmit between stations. Accordingly, it is possible to transmit the channel signal to the sub-system in the subsidiary station among the sub-systems S1 to Sn, but when additional inter-station transmission is required, a separate relay device must be added to transmit the channel signal.

However, when additional relay devices are additionally used, as many WDM devices as necessary are required to have as many relay devices as necessary for transmission between stations. This has greatly reduced the utility value of WDM devices.

In addition, an error detection test for each channel signal in the system requires the use of an instrument for each channel. This, of course, requires a separate instrument and, in practice, requires too many instruments to do so.

As described above, the conventional WDM system has a disadvantage in that a separate relay device must be added as an external additional device in order to transmit the wavelength division demultiplexed channel signal between stations. In addition, the error detection test for each channel signal in the system had to use a separate instrument for each channel.

Accordingly, an object of the present invention is to provide an inter-station transmission unit capable of transmitting a wavelength division demultiplexed channel signal between stations without using a separate relay device.

Another object of the present invention is to provide an inter-station transmission unit capable of detecting an error of a wavelength division demultiplexed channel without using a separate measuring instrument.

1 is a block diagram of a typical WDM system receiving side;

2 is a block diagram of a receiving side of a WDM system to which an inter-station transmission unit according to an embodiment of the present invention is applied;

3 is a detailed block diagram of the inter-station transmission unit 104 of FIG. 2 in accordance with an embodiment of the present invention.

In order to achieve the above object, the inter-station transmission unit of the present invention inputs one channel signal to be transmitted to a subsystem requiring transmission between stations among the channel signals separated by the wavelength division demultiplexer, converts it into an electrical signal, and then extracts data. Optical receiver module, which is connected to the optical transmission module connected to the optical receiver module and the subsystem requiring transmission, and converts the data extracted by the optical receiver module into the optical signal and transmits the optical signal to the subsystem requiring transmission between stations. And a transmitter module.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the annexed drawings, many specific details, such as specific transmission rates or demultiplexing ratios, are shown to provide a more general understanding of the invention, but these specific details are illustrated for purposes of illustration of the invention and the invention is directed to them. It is not meant to be limited. And a detailed description of known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

2 is a block diagram of a receiving side of a WDM system to which an inter-station transmission unit is applied according to an embodiment of the present invention. In the system of FIG. 1, the inter-station transmission unit 104 is added to a channel requiring inter-station transmission. will be. Therefore, the remaining components are the same as in Fig. 1, and accordingly given the same reference numerals. In addition, FIG. 2 shows a case where a channel requiring inter-station transmission is channel 2, and the inter-station transmission unit 104 may be used for each required channel.

3 is a detailed block diagram of the inter-station transmission unit 104 of FIG. 2 according to an embodiment of the present invention. The optical receiver module 200, the optical transmitter module 208, the demultiplexer 218, and the SOHP ( Section Overhead Processor) (220).

In FIG. 3, a positive intrinsic negative-photo diode (PIN-PD) 202, a limiting amplifier (hereinafter referred to as "LA") 204, a clock and data restorer (Clock & Data Recovery: "CDR") The optical receiver module 202 composed of 206 inputs and outputs one channel signal to be transmitted to a subsystem S2 requiring transmission between stations among the channel signals separated by the wavelength division demultiplexer 100. After converting to a signal, data and clock are extracted. The PIN-PD 202, which is a photodetector element, photodetects an input channel signal and converts it into an electrical signal. The LA 204 then limits amplifying the electrical signal converted by the PIN-PD 202. CDR 206 extracts the data and clock from the output signal of LA 204.

Each optical signal received through the wavelength division demultiplexer 100 is directly connected to the output of the wavelength division multiplexer 100 when the subsystem is located within the office. On the other hand, when the signal of the received channel requires inter-station transmission, the inter-station transmission unit 104 goes to the mounted shelf and enters the input of the inter-station transmission unit 104. The optical signal entered into the inter-station transmission unit 104 enters the optical receiver module 200 mounted in the inter-station transmission unit 104. Since the first demultiplexed optical output is not more than -15 dBm, the optical receiver module 200 can receive using the PIN-PD 202. This is typically possible because the optical output is amplified by the EDFA in front of the wavelength division demultiplexer 100 and then applied to the wavelength division demultiplexer 100 input. The optical signal is converted into an electrical signal by the PIN-PD 202 in the optical receiver module 200. Next, after the LA 204 is amplified to obtain a constant output regardless of the magnitude of the input signal, the clean waveform electrical data and clock are extracted from the CDR 206. The CDR 206 typically extracts a pair of complementary data and a pair of clocks.

The data of one of the extracted pairs of data is sent to the optical transmitter module 208 for transmission to the optical station 106 between stations. Laser Diode (hereinafter referred to as "LD") 212, LD Driver 210, Temperature Compensation Circuit (Automatic Temperature Control: referred to as "ATC") 214 and Automatic Light Output Control Circuit (Automatic Power) Control (hereinafter referred to as "APC") 216 is an optical transmitter module 208 is connected to the optical receiver module 200 and the inter-station optical transmission line 106 is connected to the subsystem (S2) that needs to be transmitted between stations. It is connected to the data is converted into the optical signal extracted by the CDR 206 and transmitted to the subsystem (S2). The LD 212 is driven by the LD driver 210 to oscillate an optical signal to be transmitted to the inter-station transmission path 106. The LD driver 210 corresponds to the data extracted from the CDR 206. To directly modulate the optical signal. In the optical transmitter module 208, the LD 212 has a property of changing with temperature, and an APC 216 is added to maintain a constant light output with the ATC 214. At this time, the transmission distance is determined according to the specification of the LD 212. In the application example of the present invention, an LD of 1310 nm wavelength is used for 15 km and 40 km, and an LD of 1550 nm wavelength is required when transmission of 60 km or more is required. Was used. Therefore, the desired distance can be transmitted by selecting a specification suitable for the distance required by the LD 212 in the optical transmitter module 208.

Meanwhile, another data and a pair of clocks extracted by the CDR 206 are applied to the demultiplexer 218 for error detection of the received data. Demultiplexer 218 demultiplexes data applied from CDR 206 into low-speed data that can be processed by SOHP 220. For example, if the data applied from the CDR 206 is 2.5 Gbps and the SOHP 220 is capable of 51 Mbps processing, the 1 Gbps demultiplexer chip and the 1: 3 demultiplexer chip are cascaded to provide 48 2.5 Gbps data. Demultiplexed to 51Mbps and applied to SOHP 220. The SOHP 220 uses a dedicated Application Specific Integrated Circuit (ASIC) for error detection for optical data performance testing. Accordingly, in the related art, in order to detect an error for each channel, a meter must be provided for each channel, and this role can be performed by using the inter-station transmission unit 104.

As described above, the inter-station transmission unit 104 inputs the channel signal separated by the wavelength division demultiplexer 100 and performs photoelectric conversion through the internal optical receiver module 200 to use a part of the data for error detection. The other data is used as an input of the optical transmitter module 208 to be used for inter-station transmission of channel signals. That is, one of the output data of the optical receiver module 200 is used as an input of the optical transmitter module 208, and the other electrical data is applied to the SOHP 220 after passing through the multiplexer 218 and thus the SOHP 220. By this, the error detection function of the optical signal is performed. The error detection function by the SOHP 220 is the same as in the normal case. Accordingly, by inserting a signal transmitted through the entire WDM transmission path into the station-to-station transmission unit 104 without a separate measuring instrument, the error in the transmission path can be monitored. Of course, such an error is typically processed in S / W and can be viewed on a GUI (Graphical User Interface). By using several such units, errors can be detected for each channel at the same time.

Meanwhile, in the conventional WDM system, when the data is transmitted to the sub-system through wavelength division demultiplexing, the system structure is transmitted without any additional device. In the practical application of the present invention, the inter-station transmission unit 104 can be mounted. By creating a separate shelf, the inter-station transfer function is handled as an option. In addition, the inter-station transmission unit 104 is almost similar to a conventional channel unit in terms of functionality as shown in FIG. Accordingly, if only the module form of the transmitter is changed and the structure can accommodate the rest, the unit can be compatible between the channel unit and the station-to-station transmission unit 104. That is, the function of the unit can be determined according to the module. In this way, the inter-station transmission unit 104 has many similarities to the functions of the existing channel unit, and the internal modules and the parts used are the same, so that the actual unit of the present invention has the same unit size. In addition, the optical receiver module 200 used a relatively inexpensive commercial receiver, and the optical transmitter module 208 was remanufactured to fit the inter-station transmission unit 104 in the same structure as a conventional optical transmitter module.

By adding the inter-station transmission unit 104 as described above, the inter-station transmission is not only possible, but also the desired transmission distance, which is not possible between stations by the intensity of the output of the wavelength division demultiplexer 100 which is the receiving end of the WDM system. Can be increased. In addition, by implementing a single unit without installing a separate relay device, the need for multiple system racks was made possible by only one rack. In the past, an error detection test had to use a measuring instrument for each channel, and too many measuring instruments were required to actually do this. However, the error detecting function of the inter-station transmission unit 104 can be used as a substitute for the measuring instrument. This allows performance tests on multiple channels to be performed at once, replacing the instrument in the test as well as extending the signal from the original channel receiver.

Therefore, it is possible to increase the scalability and economic aspects of the system and the network by enabling the transmission between stations without having a separate system that can be transmitted between stations to a large station with a separate relay device.

Meanwhile, in the above description of the present invention, specific embodiments have been described, but various modifications can be made without departing from the scope of the present invention. In particular, the embodiment of the present invention includes the error detection function in the inter-station transmission unit 104, but this may be omitted since it is an additional function. In this case, the demultiplexer 218 and the SOHP 220 need not be used in the inter-station transmission unit 104. Therefore, the scope of the invention should not be defined by the described embodiments, but should be defined by the equivalent of claims and claims.

As described above, the present invention has the advantage of increasing the scalability of the system and the network by allowing the transmission of the wavelength division demultiplexed channel signal between stations without using a separate relay device. In addition, errors in the wavelength division demultiplexed channel can be detected without using a separate instrument.

Claims (4)

A wavelength division multiplexing system comprising a wavelength division multiplexer for demultiplexing a wavelength division multiplexing optical signal received through a wavelength division multiplexing optical transmission path to separate optical signals for each channel and transmitting the separated channel signals to a predetermined subsystem. In An optical receiver module for inputting one channel signal to be transmitted to a subsystem requiring transmission between stations among the channel signals separated by the wavelength division demultiplexer, converting the signal into an electrical signal, and extracting data; And an optical transmitter module connected to an optical transmission path between stations connected to the optical receiver module and a subsystem requiring transmission between the stations and converting the extracted data into an optical signal and transmitting the optical signal to a subsystem requiring transmission between stations. Inter-station transmission unit. The method of claim 1, wherein the optical receiver module, A photodetecting device for photodetecting the input channel signal and converting it into an electrical signal; A limiting amplifier for limiting and amplifying the electrical signal converted by the photodetector; And a clock and a data recoverer for extracting the data and the clock from the output signal of the limiting amplifier. A wavelength division multiplexing system comprising a wavelength division multiplexer for demultiplexing a wavelength division multiplexing optical signal received through a wavelength division multiplexing optical transmission path to separate optical signals for each channel and transmitting the separated channel signals to a predetermined subsystem. In An optical receiver module for inputting one channel signal to be transmitted to a sub system requiring transmission between stations among the channel signals separated by the wavelength division demultiplexer, converting the signal into an electrical signal, and extracting data and a clock; An optical transmitter module connected to an optical transmission path between stations connected to the optical receiver module and a sub-system requiring transmission, and converting the extracted data into an optical signal and transmitting the optical signal to a sub-system requiring transmission between the stations; A demultiplexer for inputting the extracted data and a clock to demultiplex the data into low speed data; And a section overhead processor configured to detect the error by inputting the demultiplexed data. The method of claim 3, wherein the optical receiver module, A photodetecting device for photodetecting the input channel signal and converting it into an electrical signal; A limiting amplifier for limiting and amplifying the electrical signal converted by the photodetector; And a clock and data recoverer for extracting data and a clock from an output signal of the limiting amplifier.