CN2496195Y

CN2496195Y - Light relay equipment

Info

Publication number: CN2496195Y
Application number: CN01234325U
Authority: CN
Inventors: 易兴文; 张坤; 徐雁军
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2001-08-16
Filing date: 2001-08-16
Publication date: 2002-06-19
Anticipated expiration: 2011-08-16

Abstract

The utility model belongs to an optical relay equipment, which comprises a distributed Raman fiber amplifier, a first variable optical attenuator, a first erbium doped fiber amplifier, a second variable optical attenuator, a dispersion compensation module and a second erbium doped fiber amplifier, and each part is connected in sequence. The good low noise characteristic of the utility model is suitable for the multiple stage amplification during the ultra-long distance transmitting of the signal light because the utility model integrates the advantages of the FRA and the EDFA. An electric regenerator is not required when the transmission system of the optical relay equipment is used, and the complexity and the cost of the transmission system structure can be reduced.

Description

A kind of optical relay equipment

Technical field

The utility model relates to the luminous power amplification sector, especially a kind of optical relay equipment that is made of fiber amplifier.

Background technology

For realizing the long-distance transmissions of signal, existing optical transmission system generally all with erbium-doped fiber amplifier (EDFA) as TU Trunk Unit, the light signal of decaying through Optical Fiber Transmission is amplified, signal is transmitted to next stage, the span of general every grade of amplification is 80 kilometers.Because the noise of EDFA self is bigger, influenced by it, signal is after every grade of amplification, and its Optical Signal To Noise Ratio has comparatively serious deterioration, considers the requirement of receiving terminal to Optical Signal To Noise Ratio, and this optical transmission system can only pass six, 700 kilometers usually.If finish thousands of kilometers transmission, need power up relaying.

Fig. 1 is existing optical transmission system structure chart, and this optical transmission system comprises signal sending end 10, Transmission Fibers 111～114, optical relay equipment 121～124, electric trunking 13, signal receiving end 14.Signal is sent into optical fiber from transmitting terminal 10, and behind Transmission Fibers 111 transmission certain distances, because of the loss of optical fiber self, transmission signals can be attenuated, and the signal of decay amplifies the back by first optical relay equipment 121 and continues downward one-level transmission, so circulation.After what transmits, deterioration because of Optical Signal To Noise Ratio, signal can't continue downward biography, recover by 13 pairs of signals of an electric trunking this moment, the light signal of electricity trunking 13 outputs has good Optical Signal To Noise Ratio, make signal can continue, thereby realize the long-distance transmissions of light signal, arriving signal receiving terminal 14 to the next stage transmission.

Fig. 2 shows the optical relay equipment inner structure in the above-mentioned optical transmission system.Existing optical relay equipment generally all is to utilize EDFA to amplify, and is example with the optical relay equipment among Fig. 1 121, specifically comprises adjustable attenuator (VOA) 211, adjustable attenuator 212, dispersion compensation module (DCM) 23 and EDFA221, EDFA222.At first enter EDFA221 through optical fiber 111 transmission and the signal that is attenuated and amplify, make signal power obtain certain raising, enter EDFA222 through VOA212, DCM23 again and amplify once more, send into optical fiber then and carry out the next stage transmission by VOA211.Wherein EDFA221 and EDFA222 are jointly for optical relay equipment provides signal gain, with the loss of compensation Transmission Fibers 111, VOA211, VOA212, DCM23.The effect of VOA211 and VOA212 is to regulate optical signal power to satisfy EDFA221, the EDFA222 power requirement to input signal.

As known from the above, use the optical relay equipment that contains EDFA, because the noise characteristic of EDFA, the optical transmission of long distance must increase electric relaying in transmission line, has therefore increased the complexity of transmission system structure, and has increased the cost of system.

Summary of the invention

The purpose of this utility model just is to overcome the shortcoming of existing optical relay equipment, and a kind of optical relay equipment with good signal-to noise ratio is provided, and uses this optical relay equipment can reduce the complexity and the cost of system configuration in long haul optical transmission systems.

For achieving the above object, the optical relay equipment that the utility model provides comprises first adjustable optical attenuator, first erbium-doped fiber amplifier, second adjustable optical attenuator, dispersion compensation module, second erbium-doped fiber amplifier, each several part connects successively by said sequence, it is characterized in that: also comprise a Raman fiber amplifier, the output of described Raman fiber amplifier is connected with first adjustable optical attenuator.

In the above-mentioned optical relay equipment, described Raman fiber amplifier is the distributed Raman fiber amplifier, comprises the pump light source that produces pump light and described pump light and flashlight are coupled with the wavelength division multiplexer that flashlight is amplified.

In the above-mentioned optical relay equipment, described Raman amplifier comprises that further connects the isolator that described wavelength division multiplexer output is isolated echo.

In the above-mentioned optical relay equipment, described pump light source is the dual wavelength pump light source, and the pump light of its generation is the light of two different wave lengths in 1400nm～1470nm scope.

Description of drawings

Fig. 1 is existing optical transmission system structure chart;

Fig. 2 is existing optical relay equipment structure chart;

The optical relay equipment structure chart that Fig. 3 provides for the utility model;

Fig. 4 is the cut-away view of the Raman fiber amplifier among Fig. 3.

Embodiment

Below in conjunction with accompanying drawing the utility model is described further.

Shown in Fig. 1 and Fig. 2 all is prior art, and the front illustrates, does not repeat them here.

Generally within-2～0dB scope, the noise factor about the 5dB of EDFA has good low-noise characteristic to the noise factor of distributed Raman fiber amplifier (FRA) relatively, therefore is considered to realize the basis of the long Distance Transmission of without electronic relay.But the gain that Raman fiber amplifier provides signal is generally tens dB, can not compensate the decay to signal of Transmission Fibers, adjustable optical attenuator and dispersion compensation module, that is to say only to lean on FRA self to realize the relaying of light signal.Therefore, the utility model adopts the fiber amplifier of Raman, Er-doped fiber mixed structure to realize the relaying of signal, has both guaranteed the long-distance transmissions of signal, makes noise characteristic be better than traditional optical relay equipment again.

Fig. 3 shows internal structure of the present utility model, as shown in the figure, optical relay equipment comprises distributed Raman fiber amplifier (FRA ') 31, first adjustable optical attenuator (VOA) 321, first erbium-doped fiber amplifier (EDFA) 331, second adjustable optical attenuator (VOA) 322, dispersion compensation module (DCM) 34 and second erbium-doped fiber amplifier (EDFA) 332, above each several part connects successively by said sequence, and its course of work is as follows.

Flashlight part in the transmission course of Transmission Fibers is attenuated, and therefore needs the amplification of optical relay equipment.At first amplified by FRA31, FRA31 provides the gain of general 10dB.By amplifier cascade theory as can be known, the noise characteristic of first order amplifier has the greatest impact to the noise characteristic of whole amplifying unit, so signal is amplified by the low noise Raman amplifier earlier, this will determine whole amplifying unit noise characteristic to be better than making relaying with EDFA merely.Enter EDFA331 by the signal after the FRA31 amplification through VOA321 and amplify, the signal after EDFA331 amplifies enters EDFA332 by VOA322, DCM34 and amplifies, and the signal after the amplification is sent into the next stage Transmission Fibers, realizes the optical relay of a unit.Week, two discrete EDFA were from following 2 considerations: (1) DCM34 incident optical power can not be too high, otherwise can cause non-linearly, and the system transmissions characteristic is impacted; (2) in the transmission line, in a single day signal light power falls lowly excessively, just is difficult to high-quality recovery, will influence transmission performance.These 2 is contradiction, can come the seeking balance point by the distribution of EDFA331 and EDFA332 gain.By EDFA331 flashlight is amplified in advance earlier, behind dispersion compensation, amplify once more through EDFA332 again, to reach the amplification requirement of optical relay equipment through dispersion compensation module DCM34.Because optical relay equipment of the present utility model is to adopt secondary EDFA to amplify at the EDFA amplification stage, this point is consistent with traditional optical relay equipment, so no longer deep explanation.To a concrete EDFA, a specific specification is all arranged, size as input, Output optical power, make the EDFA operating characteristic satisfy specification requirement, therefore the size of determining in the time of just must making input signal light power reach design, increases by two adjustable light power attenuator VOA321 and VOA322 in optical relay equipment, to regulate the signal light power of input EDFA, make it satisfy EDFA331 and EDFA332 requirement to input optical power.

As known from the above, the difference of the utility model and traditional optical relay equipment just is to have increased a distributed Raman fiber amplifier FRA31.The distributed Raman fiber amplifier can be chosen common distributed Raman fiber amplifier.For clarity, the utility model is an example with distributed Raman fiber amplifier shown in Figure 4.

As shown in Figure 4, Raman amplifier is a distributed optical fiber amplifier, why makes distributed optical fiber amplifier be because in this fiber amplifier, and gain media is a Transmission Fibers itself; Be in the erbium-doped fiber amplifier that with the difference of erbium-doped fiber amplifier gain media is to concentrate on one section Er-doped fiber.The distributed Raman fiber amplifier comprises the wavelength division multiplexer (WDM) 41 that a pump light source 42 and are coupled pump light and flashlight, the pump light source of present embodiment is the dual wavelength pump light source, with regard to present embodiment, because of bandwidth of operation at 1529nm～1561nm, be so-called C_band (Conventional band, conventional wavelength period), just can meet the demands with the dual wavelength pump light source.If flashlight also comprises the L_band (Long band, long wave wavelength period) of 1569nm～1604nm wave band, promptly C_band and L_band signal are worked simultaneously, then also need to increase a pump light source, just can satisfy the amplification bandwidth requirement.The pump light that pump light source in the present embodiment produces is two different wave lengths in 1400nm～1470nm scope.In order to prevent the influence of echo, also be connected with an isolator (ISO) 43 at the output of wavelength division multiplexer (WDM), to ensure the operate as normal of FRA.

In distributed Raman fiber amplifier, fibre circuit itself is exactly an amplifier, and the amplification of signal is along fiber distribution rather than concentrate effect.Therefore, everywhere signal light power is all smaller in the optical fiber, thereby can reduce the signal light power of incident optical, reduces the interference of especially four wave mixing of nonlinear effect (FWM) effect, alleviate the influence of inter-channel crosstalk, this is very suitable for big capacity extra long distance optical transmission system.

The utility model combines the advantage of FRA and EDFA, and its good low-noise characteristic is suitable for the multistage amplification in the transmission of flashlight extra long distance.Use the transmission system of this optical relay equipment can not need electric relaying, therefore can reduce the complexity and the cost of transmission system structure.

Claims

1, a kind of optical relay equipment comprises first adjustable optical attenuator (321), first erbium-doped fiber amplifier (331), second adjustable optical attenuator (322), dispersion compensation module (34), second erbium-doped fiber amplifier (332), each several part connects successively by said sequence, it is characterized in that: also comprise a Raman fiber amplifier (31), the output of described Raman fiber amplifier is connected with first adjustable optical attenuator (321).

2, optical relay equipment as claimed in claim 1, it is characterized in that described Raman fiber amplifier (31) is the distributed Raman fiber amplifier, comprise the pump light source (42) that produces pump light and described pump light and flashlight are coupled with the wavelength division multiplexer (41) that flashlight is amplified.

3, optical relay equipment as claimed in claim 2 is characterized in that described Raman fiber amplifier comprises that further connects the isolator (43) that described wavelength division multiplexer (41) output is isolated echo.

4, as claim 2 or 3 described optical relay equipment, it is characterized in that described pump light source (42) is the dual wavelength pump light source, the pump light of its generation is the light of two different wave lengths in 1400nm～1470nm scope.