CN1286280C

CN1286280C - Light transmission device and method of optimum light return-to-zero code receiving pulse width

Info

Publication number: CN1286280C
Application number: CNB021287546A
Authority: CN
Inventors: 关晓龙; 常志文
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2002-08-07
Filing date: 2002-08-07
Publication date: 2006-11-22
Anticipated expiration: 2022-08-07
Also published as: CN1474521A

Abstract

The present invention relates to an optical transmission device in an optical communication system, which is used for transmitting optical return-to-zero codes. The present invention comprises a transmission link, an optical receiving module, a timing judging module, and dispersion elements arranged in front of a receiver, wherein the transmission link outputs optical return-to-zero code (RZ) pulses with narrow pulse width, which are widened by the dispersion elements; the RZ pulses are sent to an optical receiver after optimized, and are judged at a definite time after the photoelectric conversion and amplification of the optical receiving module. The present invention can optimize the shape of pulses at a receiving end of an optical return-to-zero code transmission system, and reduce the influence of timing fluctuation toward the system, so that both the stability and the sensitivity of the system are enhanced. The present invention has the advantages of simple structure and easy implementation.

Description

Optimize the light transmitting device and the method for light return-to-zero code received pulse width

Technical field

The present invention relates to the transmitting device of light in the optical communication system, is the transmission of light return-to-zero code specifically.

Background technology

In the optical communication system of at a high speed long distance, optical link sign indicating number type adopts NRZ (RZ) to improve transmission performance usually.Compare with the same rate nonreturn to zero code, the NRZ pulse is narrower, and peak power is strong, can utilize the management of dispersion management and nonlinear effect to realize long Distance Transmission.Yet for receiving terminal, burst pulse has increased difficulty regularly, is unfavorable for the raising of receiver sensitivity, and this is to need problem solving in the NRZ transmission system.Present solution concentrates in the design of optimizing Optical Receivers, and way generally all is the amplifying circuit that inserts Bezier low pass filter (LPF) or have the low pass effect after opto-electronic conversion, carries out the timing judgement after electric RZ pulse is handled again.The purpose of using low pass filter is broadening RZ pulse and the noise effect that reduces to accumulate on the circuit by restriction receiver module bandwidth, improves the nargin that digit chip is regularly adjudicated with this.Fig. 1 is the schematic block diagram of prior art scheme.

The realization difficulty of prior art scheme is that cut-off frequency is low, and then pulse stretching is effective, but can bring bigger intersymbol interference in the cut-off frequency selection of low pass filter, therefore needs integrated system to require compromise consideration.In addition, on the angle of circuit design, use the electrical filter of this processing high speed signal also can bring many problems: need to consider influences such as Insertion Loss and group delay, the cost height is in case system just is difficult to the sign indicating number type is optimized after selected certain frequency.

Summary of the invention

The purpose of this invention is to provide a kind of light transmitting device and method of optimizing light return-to-zero code received pulse width, solved the narrow problem of bringing to receiving terminal of RZ sign indicating number pulse better.The present invention is simple in structure, realizes easily, and it is used to be fit to very much RZ sign indicating number optical transmission system.

The present invention optimizes the light transmitting device of light return-to-zero code received pulse broadening, comprising:

Transmission link is used for the narrower light return-to-zero code pulse of output pulse width;

Optical pickup apparatus comprises Optical Receivers and timing judging module; Particularly, pulsewidth is carried out in this light return-to-zero code pulse widen at the preposition dispersion element of optical pickup apparatus.

Described dispersion element is positive dispersion fiber, negative dispersion optical fiber or chirped fiber grating.

The present invention includes following step:

Light return-to-zero code (RZ) pulse by the transmission link narrow output pulse width, making pulse by dispersion element pulsewidth be carried out in this RZ pulse then widens, optical pickup apparatus is delivered in RZ pulse after the optimization, through Optical Receivers and timing judging module, carries out the timing judgement then.

The preposition dispersion element of the present invention optimizes that the received pulse method can be applied to that 10Gb/s is above, in the WDM optical transmission system based on the transmission of RZ sign indicating number.In high-speed light RZ sign indicating number transmission system, receive waveform by utilizing the preposition dispersion element high-speed light of receiver RZ sign indicating number transmission system (positive dispersion fiber, negative dispersion optical fiber or chirped fiber grating) optimization, improve the timing judgement tolerance limit and the receiver sensitivity of system.

Use the present invention the adjustment of original electric territory reception pulsewidth is converted into the pulsewidth adjustment of light territory, adopt optical passive component to carry out pulsewidth and optimize and revise to entering RZ burst pulse before the receiver module, promptly before entering receiver, just solved the narrow problem of RZ pulse, thereby strengthened system's anti-jitter ability and receiver sensitivity, thereby improved transmission system nargin.This mode is simple in structure, realize easily, good stability, adjusts flexibly, thereby fundamentally overcome the shortcoming of original scheme.

Description of drawings

Fig. 1: prior art scheme schematic block diagram

Fig. 2: basic technical scheme schematic block diagram of the present invention

Fig. 3: negative dispersion optical fiber technical scheme schematic block diagram

Fig. 4: positive dispersion fiber technical scheme schematic block diagram

Fig. 5: chirped fiber grating technical scheme schematic block diagram

Among the figure: the 1-dispersion element, the 2-Optical Receivers, 3-is judging module regularly, the light pulse of 4-circuit, 5-optimizes back light pulse, 6-optical-electrical converter, the 7-Bessel filter, the 102-negative dispersion optical fiber, 103-positive dispersion fiber, 51-chirped fiber grating, 50-optical loop device, 501-optical loop device first port, 502-optical loop device second port, 503-optical loop device the 3rd port.

Embodiment

Fig. 2 has provided basic technical scheme of the present invention.The RZ pulse 4 that electrical transmission link output pulse width is narrower, by dispersion element 1 (can be positive dispersion fiber, negative dispersion optical fiber or chirped fiber grating etc.) pulsewidth being carried out in this RZ pulse widens, RZ pulse 5 after the optimization is delivered in the Optical Receivers 2, through opto-electronic conversion with after amplifying, carry out the timing judgement by 3 then.The present invention makes pulse just obtain broadening before light-to-current inversion by the preposition dispersion element of receiver module, has strengthened the resistivity (anti-jitter ability) of system to timing oscillation, has improved receiver sensitivity, thereby has improved transmission system nargin; Owing to adopted Passive Optical Components, receive pulsewidth optimization and be transformed into the processing of light territory from electric territory simultaneously, need not change, reduced the design difficulty of receiver module original electric receiver.This mode is simple in structure, the realization appearance has strengthened system's anti-jitter ability and receiving sensitivity, thereby improves transmission system nargin.

Fig. 3 has provided a specific implementation of this invention, and what the dispersion element here adopted is negative dispersion optical fiber 102, in general is dispersion compensating fiber (DCF).The core diameter area is little because the dispersion compensating fiber abbe number is big, can utilize in the optical fiber from being modulation (SPM) effect acceleration pulse broadening mutually, therefore this scheme is at circuit light pulse peak power condition with higher.Powerful circuit RZ burst pulse enters has little core in the DCF of area the time, produces very strong SPM effect, cause the RZ burst pulse of importing produce than high-chip the very fast broadening of spectrum; Simultaneously because the big chromatic dispersion of DCF, the rapid broadening of narrow RZ pulse that makes input, light pulse after obtaining to optimize among Fig. 3 enters Optical Receivers 2 opto-electronic conversion, electric pulse after the conversion also has the pulsewidth of broad like this, be equivalent to increase the timing judgement tolerance limit of system during through timing judging module 3, thereby also just improved the receiving sensitivity of Optical Receivers.Usually, because DCF has bigger abbe number, therefore adopt short length to realize.If receiving terminal fiber power is lower, also can add an image intensifer, light signal is amplified the back carry out pulsewidth optimization entering DCF, but can add certain noise like this.

Fig. 4 has provided second specific implementation of this invention, and what the dispersion element here adopted is positive dispersion fiber 103, in general can be G652 (SMF) or G655 (LEAF) optical fiber.Owing to the GVD (Group Velocity Dispersion) effect (GVD) in the positive dispersion fiber can be pressed narrow pulsewidth with the effect of SPM effect, therefore this mode is suitable for the lower situation of receiving terminal optical signal power, its operation principle and implementation are basic identical with first, just are not repeated here.

Fig. 5 has provided the 3rd specific implementation of this invention, and what the chromatic dispersion did not here have the part employing is chirped fiber grating 51, and in general, chirped fiber grating is used for carrying out dispersion compensation, i.e. compressed pulse widths.If but chirp grating is inverted the usefulness of coming, then will produce opposite dispersion characteristics, can make optical pulse broadening.Among Fig. 5, the circuit light pulse is input to first port of optical loop device 501, be input to through its second port 502 and carry out pulsewidth in the chirped fiber grating 51 and optimize and revise, the light pulse after optimizing and revising is input to photoelectricity receiver module 2 and regularly receives judgement in the judging module 3.This mode all can for receiving terminal optical signal power size cases.

Claims

1, a kind of light transmitting device of optimizing light return-to-zero code received pulse width comprises:

Transmission link is used to transmit the light return-to-zero code pulse signal;

Optical pickup apparatus comprises Optical Receivers and timing judging module; It is characterized in that:

Dispersion element is set before optical pickup apparatus, pulsewidth is carried out in described light return-to-zero code pulse widen.

2, according to the light transmitting device of the described optimization light return-to-zero code of claim 1 received pulse width, it is characterized in that: described dispersion element is a positive dispersion fiber.

3, according to the light transmitting device of the described optimization light return-to-zero code of claim 1 received pulse width, it is characterized in that: described dispersion element is a negative dispersion optical fiber.

4, according to the light transmitting device of the described optimization light return-to-zero code of claim 1 received pulse width, it is characterized in that: described dispersion element is a chirped fiber grating.

5, a kind of optical transmission method of optimizing light return-to-zero code received pulse width is characterized in that: comprise the steps:

Light return-to-zero code RZ pulse by the transmission link narrow output pulse width;

Making pulse by dispersion element pulsewidth be carried out in described RZ pulse then widens;

Optical pickup apparatus is delivered in RZ pulse after the optimization, carries out the timing judgement then.

6, according to the optical transmission method of the described optimization light return-to-zero code of claim 5 received pulse width, it is characterized in that: described dispersion element is positive dispersion fiber, negative dispersion optical fiber or chirped fiber grating.