KR20010068982A - Protocol-free optical transponder - Google Patents

Abstract

PURPOSE: A transmission speed independency optical transponder is provided to install a BRI(Basic Rate Interface) and a reference clock generator, so as to extract a clock regardless of a transmission format and a transmission speed to restore data. CONSTITUTION: A photoelectric converter(211) converts an inputted optical signal into an electric signal. A preamplifier(212) amplifies the converted electric signal. A limiting amplifier(213) amplifies the electric signal to a voltage level of a digital signal. A programmable CDR(Call Detail Record)(214) restores a clock and data according to a reference clock from the electric signal. A laser diode driver(215) outputs a modulation current. A laser diode unit(216) outputs an optical signal according to the modulation current. A BRI(Basic Rate Interface)(220) performs an exclusive OR operation relating to a delay signal delaying the electric signal as much as set time and the electric signal, and recognizes a transmission speed through the operated signals. A reference clock generator (229) generates the reference clock according to the transmission speed, and outputs the reference clock to the programmable CDR(214).

Description

Baud rate independent optical transponders {PROTOCOL-FREE OPTICAL TRANSPONDER}

TECHNICAL FIELD The present invention relates to optical transmission systems, and more particularly, to optical transponders used in wavelength division multiplexing systems.

In the optical transmission system, various protocols and corresponding bit rates may be employed. Examples include Fiber Distributed Data Interface (FDDI), Enterprise Systems CONnectivity (ESCON), Fiber Channel, Gigabit Ethernet, Asynchronous Transfer Mode (ATM), and their transfer rates are 125 Mb / s, respectively. , 155Mb / s, 200Mb / s, 622Mb / s, 1062Mb / s, 1.25Gb / s, 2.5Gb / s. As such, one protocol / transmission rate suitable for the optical transmission system is appropriately selected from among various protocols and transmission rates thereof. In the optical transmission system employing such one protocol / transmission rate, the transmission speed of the optical signal is set in advance, so that the optical transponder used in the optical transmission system is designed for the predetermined transmission rate. The optical transponder converts the input optical signal into an electrical signal, restores original data from which noise is removed from the electrical signal, and transmits the converted optical signal back to the optical signal.

1 is a view showing the configuration of a conventional optical transponder. The illustrated optical transponder includes a photoelectric converter 110, a preamplifier 120, a limiting amplifier 130, a CDR 140, a laser diode driver 150, and a laser diode 160. The photoelectric converter 110 converts an input optical signal into an electrical signal. The preamplifier 120 amplifies the electrical signal input from the photoelectric converter 110. Since the preamplifier 120 linearly amplifies the input electrical signal, the difference between the two voltage levels becomes too large when the output electrical signal is a digital signal. Thus, in the case of a digital signal consisting of a "0" level and a "1" level, the difference between the two levels is so large that it becomes impossible to extract clock and data from the CDR.

The limiting amplifier 130 located at the rear end of the preamplifier 120 serves to increase the gain of a small voltage level and to limit a predetermined voltage level or more. That is, the voltages of the "0" level and the "1" level are to maintain a constant value, respectively. The electrical signal output from the limiting amplifier 130 is input to the CDR 140. The CDR 140 reproduces data and a clock from an electrical signal input according to a single reference clock preset according to the transmission speed of the optical signal. The operation of the CDR 140 is to reshape, regenerate, and retime the input electrical signal, thereby regenerating data and clock from the input electrical signal. The data restored in the CDR 140 is used to drive the laser diode driver 150, and the laser diode driver 150 serves to supply a modulation current and a bias current according to the data to the laser diode 160. do. The laser diode 160 outputs an optical signal having a predetermined wavelength under the control of the laser diode driver 150.

Meanwhile, the optical transmission system has been converted from a time division multiplexing (TDM) scheme to a wavelength division multiplexing (WDM) scheme in which multiple channels of different wavelengths are multiplexed and transmitted simultaneously through one optical fiber. Accordingly, researches are being conducted to multiplex and transmit optical signals of various channels having various protocols and transmission rates to one optical fiber. In particular, the demand for optical transmission systems increases in urban areas. Due to the increase in data traffic, wavelength-division multiplexing systems for urban areas increase data traffic as well as SDH / SONET (Synchronous Digital Hierarchy / Synchronous Optical NETwork) format. Flexibility to simultaneously accommodate various transmission formats such as FDDI, ESCON, Fiber Channel, Gigabit Ethernet, and ATM.

However, conventional optical transponders do not know the transmission speed, and when such optical transponders are used in a wavelength division multiplexing system, they do not extract a clock for each channel, but merely perform waveform shaping, that is, reshaping and regeneration functions. Only these were performed to reproduce the optical signal. Therefore, in the above system, transmission quality is degraded by noise and timing jitter that accumulate and increase as a node passes through. In particular, when using various optical protocols and transmission speeds in optical networks for urban areas, the use of optical transponders having only the reshaping and regeneration functions described above causes a problem that the transmission distance is severely limited due to the deterioration of transmission quality. There is this.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a transmission rate independent optical transponder capable of restoring data by extracting a clock regardless of transmission format and transmission speed in an optical transmission system. In providing.

In order to achieve the above object, according to the present invention, a photoelectric converter converting an input optical signal into an electrical signal, a preamplifier for amplifying the photoelectrically converted electrical signal, and an electrical signal output from the preamplifier A limiting amplifier for amplifying to a voltage level, a programmable CDR for recovering clock and data according to a reference clock from an electrical signal input from the limiting amplifier, and a laser diode for outputting a corresponding modulation current by inputting the data. An optical transponder having a driver and a laser diode unit for outputting an optical signal according to the modulation current,

A BRI for recognizing a transmission rate through a delayed signal obtained by delaying an electrical signal input from the limiting amplifier by a predetermined time and an exclusive OR operation of the electrical signal;

And a reference clock generator for generating a reference clock according to the transmission rate recognized by the BRI and outputting the reference clock to the programmable CDR.

1 is a view showing the configuration of a conventional optical transponder,

2 is a view showing the configuration of a transmission rate independent optical transponder according to an embodiment of the present invention,

3 is a diagram showing optical power according to different transmission speeds of transmission rate independent optical transponders according to an embodiment of the present invention;

4 is a view showing the BRI of FIG.

5 is a view showing the configuration of the wavelength stabilization unit of FIG.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention; In describing the present invention, detailed descriptions of related well-known functions or configurations are omitted in order not to obscure the subject matter of the present invention.

2 is a view showing the configuration of a transmission rate independent optical transponder according to an embodiment of the present invention. The illustrated transmission rate independent optical transponder includes a signal unit 210 and a controller 220. The signal unit 210 includes a photoelectric converter 211, a preamplifier 212, a limiting amplifier 213, a programmable CDR 214, a laser diode driver 215, and a laser diode unit 216. The controller 220 includes a BRI 220 for controlling the programmable CDR 214, a reference clock generator 229, and a wavelength stabilizer 230 for stably controlling the output wavelength of the laser diode unit 216. do.

The optical signal input to the photoelectric converter 211 is input at an arbitrary protocol and transmission rate. The input optical signal is converted into an electrical signal in the photoelectric converter 211, and the preamplifier 212 amplifies the electrical signal input from the photoelectric converter 211. The limiting amplifier 213 outputs the electrical signal to the programmable CDR 214 and the BRI 220 so that voltages of the "0" level and the "1" level of the input electrical signal are maintained at constant values, respectively.

The BRI 220 analyzes an electrical signal input from the limiting amplifier 213 to recognize a transmission speed. Unlike the related art, the reference clock generator 229 includes a plurality of oscillators for generating clock signals having a plurality of different frequencies, and the reference clock generator 229 includes a transmission rate recognized by the BRI 220. The internal oscillator is selectively operated to generate a reference clock equal to. The programmable CDR 214 not only reshapes and regenerates an electrical signal but also retimes and reproduces the electrical signal according to the reference clock generated by the reference clock generator 229. The data restored in the programmable CDR 214 is used to drive the laser diode driver 215, and the laser diode driver 215 serves to supply a modulation current according to the data to the laser diode unit 216. .

The laser diode unit 216 outputs an optical signal having a predetermined wavelength according to the modulation current of the laser diode driver 215. In addition, the wavelength stabilizer 230 of the controller 220 accurately controls the wavelength of the optical signal output from the laser diode unit 216.

3 is a diagram illustrating optical power according to different transmission speeds of transmission rate independent optical transponders according to an exemplary embodiment of the present invention. In FIG. 3, although the transmission rate independent optical transponder according to the present invention outputs from 125Mbps to 1250Mbps, it is possible to output substantially up to 2.5Gbps.

4 is a diagram illustrating the BRI 220 of FIG. 2. The illustrated BRI 220 includes a baud rate recognizer 221, a filter 226, and an A / D converter 227 including a buffer 222, a delay 223, and an operator 224. And a transmission rate determining unit 225 composed of the determiner 228. The operation of the transmission rate recognition unit 221 will be described below. When an electrical signal of a specific transmission rate, that is, a specific pulse period, is input, a delay signal that is somewhat delayed by the delay unit 223 is generated. The electrical signal and the delay signal are the exclusive OR operation of the calculator 224 to generate a recognition signal. At this time, the recognition signal is represented by a plurality of pulses having a section at the high level of the same interval as the delay time. Through this process, a difference in the number of pulses of the recognition signal is generated according to a difference in the transmission speed of the input electrical signal, and the difference is almost proportional to the transmission speed.

Therefore, by analyzing the recognition signal, the number of pulses generated in a predetermined time in the recognition signal is confirmed, and thus, the transmission speed can be grasped. However, the maximum transmission rate currently employed in the optical transmission system is a unit of Gb / s, and the circuit configuration is difficult to directly count the number of pulses of the recognition signal in the electric signal of the transmission rate. Accordingly, the transmission rate determining unit 225 according to an embodiment of the present invention determines the transmission rate through the voltage level output by low-pass filtering the recognition signal.

The operation of the transmission rate determining unit 225 will be described below. The filter 226 receives the recognition signal output from the calculator 224 of the recognition signal generator 221 and outputs the low pass filtering. The A / D converter 227 digitally converts the analog output of the filter 226, and the voltage level of the digital signal increases linearly with the transmission speed. The determiner 228 determines the transmission rate of the digital signal by identifying the voltage level.

5 is a diagram illustrating a configuration of the wavelength stabilizer 230 of FIG. 2. The illustrated wavelength stabilizer 230 operates by dividing into a normal mode or a blocking mode. The normal / blocking mode switch is determined by user input. The user input is made through an external interface, and the user input is output to the microprocessor 233 through an external interrupter 235. The microprocessor 233 outputs a bias control signal for operating the laser diode unit 216 regardless of the normal / blocking mode. The microprocessor 233 outputs an on signal to a switch 238 when the user input is a normal mode signal. The on signal causes switch 238 to open. The bias control signal is input to a digital-to-analog converter 237, converted into an analog signal, and applied to the bias circuit 239 through an open switch 238. The bias circuit 239 outputs a bias current according to the bias control signal to the laser diode unit 216. The laser diode unit 216 is composed of a DFB laser diode, a temperature controller with a thermometer, an etalon filter, and two photodiodes. The DFB laser diode emits light having a constant emission angle. The etalon filter transmits the light incident from the DFB laser diode at a transmittance according to the wavelength and the incident angle. Adjacent pairs of photodiodes detect only light in a certain region of the light transmitted from the etalon filter. The angle that the etalon filter makes with the optical axis is set so that the intensities of the light incident on the photodiodes are the same with respect to the normal oscillation wavelength of the DFB laser diode. Accordingly, the wavelength shift detection signals PD1 and PD2 output from the photodiodes become a function of the wavelength of incident light, respectively. That is, the transmittance in the etalon filter of the light incident on the photodiode is a function of the angle of incidence and the wavelength, but since the angle of incidence is fixed, it is a function of only the wavelength of the incident light. The wavelength shift detection signals PD1 and PD2 are input to an analog-to-digital converter 232 and converted into a digital signal. The microprocessor 233 receives the wavelength shift detection signals PD1 and PD2 and outputs a temperature variable signal corresponding to the level difference between the wavelength shift detection signals PD1 and PD2. That is, when the level difference between the wavelength shift detection signals PD1 and PD2 is '0', it means that the oscillation wavelength of the DFB laser diode is stabilized. In addition, when the level difference between the wavelength shift detection signals PD1 and PD2 is not '0', the microprocessor 233 feeds back a temperature variable signal for stabilizing the oscillation wavelength of the DFB laser diode to the temperature controller. Let's do it.

According to the temperature variable signal, the temperature controller stabilizes the oscillation wavelength of the DFB laser diode by adjusting the operating temperature of the DFB laser diode. That is, the operating temperature of the DFB laser diode is adjusted to a temperature corresponding to the stabilization wavelength so that the oscillation wavelength of the DFB laser diode is shifted to the stabilization wavelength. The thermostat also includes a thermometer, such as a thermistor thermometer. The temperature controller adjusts an operating temperature of the DFB laser diode and simultaneously outputs a temperature sensing signal generated by sensing the operating temperature of the DFB laser diode in the thermometer. The temperature detection signal is input to the A / D converter 232 and converted into a digital signal, and the temperature value output from the A / D converter 232 is input to the microprocessor 233.

When the user input is a cutoff mode signal, the microprocessor 233 stores the temperature value in an electrically erasable and programmable ROM (EEPROM) 234, and outputs an OFF signal to the switch 238.

The bias control signal output from the microprocessor 233 is cut off by the switch 238 in the closed state, and the DFB laser diode is shut down because the bias circuit 239 does not output a bias current. At this time, the wavelength shift detection signals PD1 and PD2 do not exist at the same time as the DFB laser diode is shut down, but the temperature controller continues to output the temperature detection signal. The microprocessor 233 switches to the blocking mode and simultaneously holds the temperature of the DFB laser diode based on the temperature value stored in the EEPROM 234.

That is, the microprocessor 234 compares the temperature value input from the A / D converter 232 with the temperature value stored in the EEPROM 234, and converts the temperature variable signal corresponding to the temperature difference into the temperature controller. Output The temperature controller changes the temperature of the laser diode to a corresponding temperature variable width in response to the temperature variable signal. Thus, the temperature of the DFB laser diode is held at the temperature stored in the EEPROM 234.

As described above, the optical transponder according to the present invention has the advantage that the BRI and the reference clock generator can recover the data by extracting the clock regardless of the transmission format and transmission speed in the optical transmission system.

Furthermore, the optical transponder according to the present invention has an advantage that the wavelength of the optical signal outputted can be stably controlled by providing the optical wavelength stabilizer.

Claims (6)

A photoelectric converter for converting an input optical signal into an electrical signal, a preamplifier for amplifying the photoelectrically converted electrical signal, a limiting amplifier for amplifying the electrical signal output from the preamplifier to a voltage level of a digital signal; A programmable CDR for restoring clock and data according to a reference clock from an electrical signal input from the limiting amplifier, a laser diode driver for outputting a corresponding modulation current by inputting the data, and an optical signal according to the modulation current In the optical transponder comprising a laser diode unit, A BRI for recognizing a transmission speed through a delayed signal delaying the electrical signal received from the limiting amplifier by a predetermined time and an exclusive OR of the electrical signal and calculating the calculated signal; And a reference clock generator for generating a reference clock according to the transmission rate recognized by the BRI and outputting the reference clock to the programmable CDR. The method of claim 1, And a wavelength stabilizer for stabilizing an output wavelength of the laser diode unit. The method according to claim 1 and 2, The BRI delays the electrical signal, compares the original electrical signal with time zones, and generates a recognition signal to generate a recognition signal. The transmission rate determines a transmission rate through a low level filtering output of the recognition signal. A transmission rate independent optical transponder, characterized in that it comprises a determination unit. The method of claim 3, The recognition signal generation unit separates and outputs the received signal into two signals identical to the received signal, a delay unit for delaying and outputting one of the outputs of the buffer by a predetermined time, and a reception delayed by the delay unit. Comprising an exclusive OR operation of the signal and the original received signal to output a recognition signal, The transmission rate determining unit receives a recognition signal output from the calculating unit of the recognition signal generator, and outputs the filter by low pass filtering, an analog / digital converter for digitally converting the analog output of the filter, and the analog / digital converter A transmission rate independent optical transponder, characterized in that it is configured to determine the transmission rate by receiving the output. The method of claim 2, The laser diode unit includes a laser diode whose oscillation wavelength changes with temperature, and wavelength shift detection signals indicating a level difference corresponding to a shift value of the oscillation wavelength of the laser diode and temperature sensing indicating an operating temperature of the laser diode. Generating a signal, and adjusting an operating temperature of the laser diode according to a temperature variable signal, The wavelength stabilizing unit generates a memory unit for storing a temperature value, a shut-off mode signal for shutting down the laser diode, an external interrupter connected to an external interface, and a temperature variable signal corresponding to a level difference between the detection signals. Outputs to the laser diode unit, stores the temperature value indicated by the temperature detection signal when the cutoff mode signal is applied from the external interrupter, and stores the temperature of the laser diode according to the temperature value stored in the memory unit. A transmission rate independent optical transponder, characterized in that it consists of a holding microprocessor. The method of claim 5, The laser diode is a transmission rate independent optical transponder, characterized in that the DFB laser diode.