JPH1146165A - Optical communication system and optical amplifier system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid stimulated power from being 50% or less on the occurrence of a fault in an optical fiber of the optical communication system having two optical fibers in comparison with an optical communication system having 2-stage optical amplifiers on two communication wires. SOLUTION: This system is provided with a 1st transmitter that sends at least one signal through a 1st optical fiber 802, a 2nd transmitter that sends at least one signal through a 2nd optical fiber 804, 2-stage amplifiers off the 1st and 2nd lines, laser pumps 814, 816, 818, 820 that provide a stimulation signal to the two stage amplifiers, a 1st receiver that receives a signal from the 1st optical fiber and a 2nd receiver that receives a signal from the 2nd optical fiber. In this case, a single system providing the 1st stimulation signal at least one stage of the amplifier of the 1st and 2nd lines is formed by the laser pumps.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optically amplified optical communication system and optical amplification system comprising two optical fiber lines, and an optical communication system having improved reliability. System or method of optical amplification system.

[0002]

2. Description of the Related Art In recent years, optically amplified long distance optical communication systems have become increasingly popular. In practice, in long-haul communication systems, periodic optical amplifiers have been used as an attractive alternative to opto-electronic converters and regenerators / repeaters to eliminate signal attenuation. As a result, there has been much interest in developing extremely reliable and low cost optical amplification systems.

[0003] This reliability is especially important when the communication system is not easily accessible, such as when used underwater.

In order to enable high-quality optical amplification at a relatively low cost, optical amplification fibers doped with rare earth metals have been developed. Excellent results have been obtained with erbium-doped fibers among the doped amplification fibers. Energy is provided to the doped optical fiber using a laser pump. The doped amplification fiber and laser pump can be integrated into an optical fiber using a wavelength division multiplexer (WDM). The pump laser excites the rare earth ions to higher energy levels through the conversion of the rare earth ions to form a suitable amplification medium. This causes amplification of the signal on the input side of the erbium-doped amplification fiber by the induced emitter.

[0005] Since the laser pump is the only active component in the amplification system, the laser pump is likely to degrade or fail. When such a failure occurs, the optical amplifier, and thus the optical communication system, may be inoperable. To eliminate such drawbacks, several techniques have been developed to design an optical communication system that can limit the effects of laser pump failure or deterioration.

[0006] To alleviate optical amplifier failures, a number of redundancies have been suggested.

US Pat. No. 5,173,957 to Bergano and others relates to the redundancy of laser pumps to fiber optic amplifiers, in which a 3 dB optical coupler is used. At least two laser diodes are coupled via this, and pump power is simultaneously supplied to each of the two single-stage fiber optic amplifiers (FIG. 8 attached). If one of the laser diode pumps fails, the other laser diode pumps provide power to each of the fiber optic amplifiers. Thus, if one laser pump fails, the pump power of each of the two single-stage optical fiber amplifiers will be reduced by 50%.

US Pat. No. 5,241,414 to Giles and others discloses that pump beams from a laser train are mixed together by a star coupler to form a plurality of composite pump beams. A group of optical amplifiers to form is disclosed. Each of these composite pump beams is distributed to the pump port of one particular optical amplifier in the group of optical amplifiers.

[0009] US Patent No. 5,253,104 to Delavaux discloses a balanced doped optical fiber amplifier. FIG. 7 shows an amplifier consisting of a first stage of a preamplifier and a second stage of a power booster arranged in stages along the same optical fiber line. In this configuration, the pump signal is distributed and combined between the first and second stages using a common pump source to enable a conservative arrangement.

[0010] Published UK Patent No. 2,272,202
No.-A discloses a diode-pumped optical fiber amplifier in which the amplification fiber is split into two parts and there are two amplifier stages, both pumped by a laser diode. A second diode may be included for redundancy, the outputs of which are combined via a pair of polarizing beam splitters / combinations.

Published International Patent Application No. 92/0564
No. 2 discloses an optical fiber amplifier having one or more working fibers coupled to an optical communication line such that each of the working fibers has at least one input for a pump signal. The fiber optic amplifier includes an optical combination network having a plurality of inputs coupled to respective pump lasers. The output of the combinational network is coupled to a pump signal input on a workable fiber.
The circuitry is adapted to combine the optical energy added from the pump lasers, and several pump lasers generate optical energy at each one of the outputs of the combined circuitry.

As a further refinement of the solution described above, in the case of a two-stage optical amplifier, reliability can be obtained with two laser pumps. Each of the laser pumps is connected to both stages of the optical amplifier described above. As illustrated in FIG.
The optical amplifier for the optical fiber 402 includes a first-stage amplification fiber 404, a second-stage amplification fiber 406, and a first W
DM 408, second WDM 410, coupler 412
And laser pumps 414 and 416. In this case, the excitation signals from the laser pumps 414, 416 are:
Coupled by a coupler 412, which distributes the combined excitation signal to first stage 404 and second stage 406 via WDMs 408,410. First WDM4
08 interconnects the optical fiber 402 with the excitation signal. In this way, the first-stage amplification fiber 404 is excited, and thus the signal received from the optical fiber 402 is amplified. Similarly, the second WDM 410
Receives the excitation signal, which excites the second stage amplification fiber 406. Therefore, the second-stage amplification fiber 406 amplifies the signal received from the first-stage amplification fiber 404.

However, in the above amplifier, 1
If one laser pump fails, the pump power will be reduced by 50%.

[0014]

SUMMARY OF THE INVENTION The present invention provides some additional advantages over a two line optical communication system in which each of the communication lines is provided with a two stage optical amplifier as shown in FIG. An object of the present invention is to limit the above-mentioned 50% reduction in pump power in each optical fiber line of an optical communication system including two optical fiber lines without requiring cost.

[0015] More specifically, one object of the present invention is to provide:
Two optical fiber lines, a first transmitter transmitting at least one signal over a first optical communication line, and a second transmitter transmitting at least one signal over a second optical communication line; At least one two-stage amplifier in each of the first and second communication lines, a laser pump for providing an excitation signal to the stages of the amplifier, and a first receiver for receiving a signal from the first optical communication line. And a second receiver for receiving a signal from the second optical communication line, such that a possible failure of one laser pump limits the drop in pump power in each of the fiber optic lines to no more than 50%. To improve the reliability of an optical communication system so as to increase the reliability in a simple manner.

A second object of the present invention comprises two fiber optic lines, at least one two-stage amplifier in each communication line, and a laser pump for providing an excitation signal to said stages of the amplifier. Improving the reliability of an optical communication system so as to increase reliability in such a way that a possible failure of one laser pump limits the reduction in pump power in each of the fiber optic lines to no more than 50%. is there.

A third object of the present invention comprises two optical fiber lines, at least one two-stage amplifier in each communication line, and a laser pump for providing an excitation signal to said stages of the amplifier. In an amplifier, an amplifier is improved so that gain loss and noise increase due to laser pump failure are substantially limited.

Yet another object of the present invention is to provide an optical communication system having first and second fiber optic lines, wherein a possible failure of one laser pump reduces the pump power in each of the fiber optic lines by 50%. A method of providing a laser excitation signal in an optical communication system to be limited to less than or equal to%.

[0019]

The above and other objects are achieved by the optical communication system, amplification system and method described below.

[0021] The above purpose is to achieve
It has been found that this can be achieved by providing a single laser excitation system that provides a first excitation signal to at least one of the stages of the amplifier.

Accordingly, one object of the present invention is to provide at least one optical fiber line and at least one optical communication line through a first optical communication line.
A first transmitter for transmitting one signal, a second transmitter for transmitting at least one signal over a second optical communication line, and at least one second transmitter for each of the first and second communication lines. A stage amplifier, a laser pump for providing an excitation signal to the stage of the amplifier, a first receiver for receiving a signal from a first optical communication line, and a second receiver for receiving a signal from a second optical communication line. Improving the reliability of an optical communication system comprising a receiver, wherein the laser pump is provided in at least one stage of the at least one amplifier of each of the first and second communication lines. On the other hand, it forms a single system for providing a first excitation signal.

Preferably, the system further provides a second excitation signal to another stage of the at least one amplifier of the first and second communication lines.

More preferably, there are at least four laser pumps.

A second object of the present invention is to provide two optical fiber lines, at least one two-stage amplifier in each communication line,
Improving the reliability of an optical amplification system comprising a laser pump for providing an excitation signal to said stage of said amplifier, said improvement comprising: To form a single system for providing a first excitation signal to at least one stage of each at least one amplifier.

Preferably, the system further provides a second excitation signal to another stage of the at least one amplifier on each of the first and second communication lines.

More preferably, there are at least four laser pumps.

Yet another object of the present invention is a method for providing a laser excitation signal in an optical communication system comprising first and second optical fiber lines, comprising: a) first and second laser excitation signals; B) combining the first and second laser excitation signals to form first and second output signals; and c) generating third and fourth laser excitation signals. And d) combining said third and fourth laser excitation signals to form third and fourth output signals, wherein: 1) the first and second output signals are Being provided to one of the first and second stages of the first fiber optic amplifier and being provided to one of the first and second stages of the second fiber optic amplifier; 2 Iii) third and fourth output signals correspond to said first optical fiber; Is supplied to the other of the first and second stage of the amplifier Bas line,
And providing the other of the second fiber optic line amplifier to the other of the first and second stages.

The first and third output signals are combined to form fifth and sixth output signals, while the second and fourth output signals are combined with the seventh and eighth output signals. And each of the fifth, sixth, seventh and eighth output signals is provided to a single stage of an amplifier.

[0029]

BRIEF DESCRIPTION OF THE DRAWINGS The invention can be more completely understood by reading the following description of a particular exemplary embodiment thereof, taken together with the accompanying drawings, in which: FIG.

The known optical amplification system of FIG. 8 according to US Pat. No. 5,173,957 uses a first optical fiber line 30.
2, a second optical fiber line 304, first and second amplification fibers 306 and 308, and first and second WDMs 3
10, 312, coupler 314, laser pump 31
6, 318. Laser pump 316, 318
Provides an excitation signal that is combined by coupler 314. The combined excitation signal is distributed from coupler 314 via first and second WDMs 310, 312 to first and second amplification fibers 306, 308, respectively.
Thus, the signals of the first and second optical fiber lines can be amplified respectively.

In this system, the laser pump 31
If one of the 6, 318 fails, the remaining laser pumps continue to pump the amplification fibers 306, 308.
If the power of the remaining laser pumps remains the same (high-temperature standby mode with reduced performance), the pump power of each optical amplifier will be reduced if the laser pump fails. Alternatively, the optical amplification system may be operable without reducing the pump power by increasing the power of the remaining laser pump (hot standby mode with no degradation). However,
In this case, the power of the laser pump would need to be approximately doubled.

However, if one laser pump fails, the pump power in each amplification fiber will be 50%
descend.

The optical amplification system shown in FIG. 2 has two optical fiber lines 502 and 504, amplification fibers 506 and 508 for the first optical communication line 502, and amplification fibers 510 for the second optical communication line 504. , 512, wavelength division multiplexers (WDM) 514, 516, 518, 520, couplers 522, 524, laser pumps 526, 528,
530 and 532.

In this case, the outputs of the laser pumps 526, 528 are coupled by a coupler 522. Coupler 5
22 are coupled to WDMs 514, 520
To excite the amplification fibers 506 and 512, respectively. Further, the outputs of laser pumps 530, 532 are coupled by coupler 524. The combined excitation signal from coupler 524 excites amplifier fibers 508, 510 via WDMs 516, 518, respectively. Therefore, the excited amplification fibers 506, 508
Amplifies the signal received from the optical fiber 502, and the excited amplification fibers 510 and 512 amplify the signal received from the optical fiber 504. The optical amplification system of FIG. 2 is suitable for amplifying signals propagating in both directions through optical fiber lines 502 and 504.

In FIG. 3, the optical fiber line 502 functions as a feed line, while the optical fiber line 504 functions as a return line.

In this case, the optical amplification system further includes optical insulators 634 and 636 for transmitting an optical signal only from the first stage to the second stage in each of the two-stage amplifiers. These insulators 634, 636 substantially transmit the signal and substantially block the propagation of the light beam in the opposite direction. In addition, with currently available insulators, for example, 980n
If excitation wavelengths outside the transmission band of the insulators m are used, these insulators can block the communication line for the excitation light. These insulators 634, 636 are located between the first and second amplifier stages of each fiber optic line to reduce noise and gain performance by reducing counter-propagating ASE. To the maximum. in this case,
Although not shown, one of the amplifiers has a co-propagating pump in the first stage and an opposing propagating pump in the second stage, and the insulator comprises two pumps. Is further prevented.

Further description regarding the use of insulators in optical amplifiers can be found in US Pat. No. 5,204,923.
And SPIEvol. 1789 fiber laser source and amplifier (Fiber Laser Sources a
nd Amplifiers) IV (1992), 14
M.P. on page 5-154. N. Zelvas
s), R.I. I. Laming, and D.E.
N. "Efficient Erbium-Doped F Efficient Erbium-Doped Fiber Amplifier with Integrated Optical Insulator," published by Payne.
ibre Amplifiers Incorpora
ting an Optical Isolat
r) ".

Instead of the optical insulators 634 and 636, or
Using known means in accordance with known techniques in combination with one or both of these optical insulators 634, 636, those skilled in the art will embody the requirements for specific embodiments of the invention. be able to. Examples of such means include, for example, unidirectional means such as optical circulators,
Filter means, such as a filter for removing SE, selective or time-selective multiplexing / selection for selectively adding optical signals to and reducing optical signals from the communication line.
Demultiplexing means and dispersion correction means for correcting wavelength dispersion. The means described above can be combined. For example, an optical circulator may be used in combination with a filter, multiplexer / demultiplexer and / or dispersion compensator.

The amplification fibers 506, 508, 51 shown in FIG.
Numerals 0 and 512 are erbium-doped fibers. In one example, the amplification fiber has a core doped with germanium erbium (Ge / Er).
3 is a silicon dioxide fiber having a diameter of 3. Erbium functions as an active dopant. If the Er concentration in the core of the optical fiber causes a signal loss of 7 dB / m in the above-mentioned state, for example, by using an amplifying fiber of about 17 m in length, an appropriate value for the combined first and second stages is obtained. Amplification is performed.

As disclosed in FIG. 3, signals S _in and S
_out can be a single channel or multiple channels (eg,
For WDM) transmission, it includes one or more discrete wavelengths selected in the active dopant amplification band of the fiber.

Laser pumps 526, 528, 530, 5
32 is preferably a laser diode pump that generates an excitation signal at a preselected excitation wavelength. While other wavelengths can be selected, the erbium-doped fiber in the example of FIG. 3 is pumped by the 980 nm pump signal. In the experiment described above, 15
A single channel at a wavelength of 36 nm was transmitted.

An excitation wavelength of 980 nm provides relatively high gain with low noise in erbium-doped fibers. Alternatively, for example, one for the excitation pump
480 nm may be used. The wavelength of the excitation signal is generally shorter than the signal, while other wavelengths can be used for the signal and the excitation signal.

Although different splitting ratios can be selected as appropriate, in this preferred embodiment the coupler 52
2, 524 are 3 dB couplers, so that the coupled excitation signals flowing from coupler 522 are equal to each other,
The combined excitation signals flowing from coupler 524 are also equal to each other.

The positions of the corresponding amplifying fiber and WDM can be configured to be excitable in the same direction with respect to the direction of the signal or in the opposite direction. That is, the directions of the excitation signal and the signal can be the same or opposite. FIG. 3 shows a state where all the amplification fibers are excited in the same direction. Further, the excitation direction of each respective stage of each two stage amplifier can be different.

A pair of coupled laser diode pumps 526,
528, or 530, 532, can be operated in one of two modes in the preferred embodiment: a hot standby mode with reduced performance, or a hot standby mode with no reduced performance. That is, if one laser diode pump fails in the high-temperature standby mode in which the performance is degraded, the remaining laser diode pumps continue to operate at the same power level. In the hot standby mode, where performance does not degrade, the power of the rest of the coupled laser diode pair increases to compensate for the loss.

Table 2 shows the results of experiments performed with the optical amplification system of FIG. 3 consisting of two stages of amplifiers for each of the optical fiber lines, operating in a high-temperature standby mode with reduced and no performance degradation. 1 and Table 2. In this case, the gain G along the first and second two-stage amplifiers
1, G2 are shown in logarithmic dB units. In Table 1, if one laser pump fails (P _p2 =
0), for small signals, the maximum gain loss is about 2.5d
B and when the amplifier is operating in saturation, about 3
dB, while the maximum noise rise is about 0.5 dB.
It is. The slight difference in gain loss is dependent on the corresponding performance difference in the first stage amplification fibers 506, 510 when compared to the second stage amplification fibers 508, 512. Thus, the gain loss differs slightly depending on the pump power reduction for the first or second stage.

To evaluate the advantages of the present invention, additional experiments were performed with the known amplification system of FIG. Relevant results are summarized in Tables 4 and 5 and show the performance of the optical amplification system of FIG. 8 when operating in a degraded and a hot standby mode where performance is not degraded, respectively. In this case, the gains G1, G2 along the first and second stages of the one-stage amplifier are shown in log dB units. Table 4
From when one laser pump fails (P _p2 =
0), for small signals, the gain loss is about 5 dB,
When the amplifier is operating in saturation, the increase in noise value is about 1 dB for small signals and about 1.5 dB when the amplifier is operating in saturation.
It can be seen that it is dB.

Comparing with the data in Table 4, the performance of the amplification system of FIG. 3, according to the first preferred embodiment of the present invention, is at least about 2 dB better in terms of gain loss if the laser pump fails. It can also be seen from the data in Table 1 that the noise value is superior by at least about 0.5 dB.

The optical amplification system of FIG. 4 operates in a manner similar to the first embodiment, with the only difference that
The coupler 722 is connected to the amplification fibers 706 and 710 via WDMs 714 and 718, respectively, and the coupler 724 is connected to the amplification fibers 708 and 712 via WDMs 716 and 720, respectively.

In the second embodiment, an insulator is preferably provided by a method similar to the method shown in FIG.

Further, when the optical fiber lines 702, 704 act as feed and return lines, respectively, the first stage amplification fibers 706, 710 are excited by the same combined excitation signal in the output from the coupler 722, Second stage amplification fibers 708, 712 are excited by the same combined excitation signal in the output from coupler 724. Therefore, when the laser pump fails, the pump power in both the first-stage amplification fibers 706 and 710 or the second-stage amplification fibers 708 and 712 of both two-stage amplifiers decreases. This means that two fiber lines
The stage amplifiers have exactly equal gain losses because the performance of the first stage amplification fibers 706, 710 is equal to each other and the second stage amplification fibers 708, 71
2 are equal to each other, but when compared with the respective second stages (708, 712), the respective first stages (706, 71)
This is because the performance of 0) is slightly different.

In the third embodiment shown in FIG. 5, two optical fiber lines 802 and 804, amplification fibers 806 and 808 for the first optical fiber 802, and the second optical fiber 80
4 and the laser pump 8
14, 816, 818, 820 and couplers 822, 8
24, 826, 828 and WDMs 830, 832, 83
4,836.

In this case, the laser pumps 814, 816,
The outputs of 818 and 820 are combined by couplers 822 and 824, respectively. On the other hand, the first combined excitation signal from coupler 822 and the first combined excitation signal from coupler 824 are combined by coupler 826 while
The second combined excitation signal from coupler 822 and the second combined excitation signal from coupler 824 are combined by coupler 828. Next, the excitation signals from couplers 826, 828 can be combined in any desired combination to the respective W
This third embodiment, which enters amplification fibers 806, 808, 810, 812 via DMs 830, 832, 834, 836, is also suitable for amplifying signals propagating in both directions through fiber optic lines 802, 804. ing.

In the embodiment disclosed in FIG. 6, the optical fiber line 802 functions as a feed line, while the optical fiber line 804 functions as a return line.

In this case, the optical amplifying system comprises an insulator 9
38 and 940 are further provided. In this preferred embodiment, the insulators 938, 940 completely transmit the signal while blocking noise traveling in the opposite direction. As described for the first embodiment, an insulator 93 is provided between the first and second amplifier stages of each fiber optic line.
8, 940 are arranged.

The amplification fibers 806, 808, 81 shown in FIG.
Numerals 0 and 812 are fibers doped with erbium as described above. The erbium-doped fiber of FIG. 6 is pumped by the pump signal. In this way,
This signal is amplified by the induced emitter in the amplification fiber.

As shown in FIG. 6, the signals S _in and S
_Out preferably comprises one or more discrete wavelengths selected within the active dopant amplification band of the fiber.
Further, laser pumps 814, 816, 818, 820
Is a laser diode pump that generates an excitation signal at a preselected excitation wavelength. While the erbium-doped fiber of FIG. 6 is pumped with a 980 nm pump signal, other wavelengths can be selected as described above. The wavelength of the excitation signal is generally shorter than the signal.

In this preferred embodiment, couplers 822, 824, 826, 828 are coupled to coupler 826,
The combined excitation signals flowing from 828 are equal to 3
It is a dB coupler.

Furthermore, the positions of the corresponding amplifying fibers and WDM can be designed to be excitable in the same or opposite direction with respect to the direction of the signal. That is, the directions of the excitation signal and the signal can be equal or opposite.
Further, the excitation direction of each stage of each two-stage amplifier need not be the same. For example, FIG.
8, 812 are excited in the same direction and the amplification fiber 80
6, 810 are shown excited in opposite directions.

In this third embodiment, a pair of coupled laser diode pumps 814, 816, 818, 82
0 operates in one of two modes, a hot standby mode with reduced performance or a hot standby mode with no reduced performance. That is, in the high-temperature standby mode in which the performance is reduced, when the laser diode pump fails, the remaining laser diode pumps continue to operate at the same power level. On the other hand, when one laser diode pump fails in the high-temperature standby mode in which the performance does not decrease, the power of at least one remaining laser diode pump is increased so as to compensate for the loss.

Preferably, the power of all the remaining laser diode pumps in the system is increased to compensate for the losses. This arrangement allows the laser pump to operate with less drive current than when only the power of the rest of the coupled laser pump pair is increased.
In this way, the lifetime of the laser is increased and the reliability of the communication system is increased.

The performance of the optical amplification system of FIG. 6 is shown in Table 3 which shows the experimental results when operated in a high-performance standby mode with reduced performance, in this case the first and second two-stage amplifiers. Are shown in units of dB. 1
When two laser pumps fail (P _p2 = 0), the gain drops by 1 dB for small signal gains, and by 1.5 dB when the amplifier is operating in saturation, while maximizing noise. The increase in value is about 0.5 dB.

Comparing with the data in Table 4, if one laser pump fails, the gain improvement obtained by the amplification system of FIG. 6 is about 2 in accordance with the third preferred embodiment of the present invention. It can be seen from the data in Table 3 that while the noise level is in the range of about 0.5 dB to about 4 dB, the improvement in noise value is in the range of about 0.5 dB to about 1 dB.

In FIG. 7, a receiver / transmitter station 1002 receives and transmits fiber optic signals on fiber optic lines 1004, 1006. Each of the receivers / transmitters 1002 includes both receivers and one or more optical channels, and fiber optic lines 1004, 1006.
Can send signals in both directions.
In this case, the amplifier must be in a form that can be operated in both directions.

Alternatively, the receiver / transmitter station 1002 at one end of one optical fiber line may have one or more receivers and the receiver / transmitter station at the other end of the optical fiber line. 1002 may have one or more transmitters. In this case, the optical fiber line 100
4, 1006 each transmit signals in only one direction.
The two lines can operate in the same direction or function as feed and return lines, respectively.
In any case, the receiver / transmitter of station 1002 may be capable of transmitting one or more independent optical channels. These channels are, for example, W
Multiplexing can be done by any known means such as DM, TDM or polarization multiplexer means. This optical communication system includes an optical amplification system 1008 for amplifying a signal.
Is further provided. The optical amplification system 1008 is preferably of any of the types described herein.

Although described above with respect to two independent optical communication lines, the present invention contemplates, for example, placing two amplifiers together so as to form a bidirectional amplifier operating on bidirectional optical communication lines. Also applies.

Furthermore, a pair of amplifiers comprising two communication lines according to the invention forms a single device and can easily be accommodated in a single case. This allows for a more compact communication system design.

It will be apparent to those skilled in the art that various modifications and variations can be made to the optical amplification system of the present invention without departing from the spirit or scope of the invention. For this reason, the present invention is intended to cover the above modifications and variations.

Table 1 Results of the system according to FIG. 3 in the “hot standby” mode with reduced performance [dB] Laser pump state Small signal gain G 1 = 35 I _p1 = 150 mA; P _p1 = 18 mW (P _in = − _{45dBm) G2 = 35 I p2 =} 150mA; P p2 = 18mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = 18mW G1 = 33,5 I p1 = 150mA; P p1 = 18mW G2 = 32, _{5 I p2 = 0mA; P p2} = 0mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = gain of 18mW saturation signal _{G1 = 24 I p1 = 150mA;} P p1 = 18mW (P in = -15dBm _{) G2 = 24 I p2 = 150mA} ; P p2 = 18mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = 18mW G _{= 22 I p1 = 150mA; P} p1 = 18mW G2 = 21 I p2 = 0mA; P p2 = 0mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = noise level 18mW small signal <6 I _p1 = 150 mA; P _p1 = 18 mA (P _in = −45 dBm) I _p2 = 150 mA; P _p2 = 18 mW I _p3 = 150 mA; P _p3 = 18 mW I _p4 = 150 mA; P _p4 = 18 mW <6.5 I _p1 = 150 mA; _{P p1 = 18mW I p2 = 0mA} ; P p2 = 0mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; noise level P _p4 = 18 mW saturation signal _{<6,5 I p1 = 150mA; P} p1 = 18mW ( _{P in = -15dBm) I p2 =} 150mA; P p2 = 18mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = 18mW <7 I p1 _{150mA; P p1 = 18mW I p2} = 0mA; P p2 = 0mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = 18mW

Table 2 Results of the system according to FIG. 3 in “hot standby” mode with no performance degradation [dB] Laser pump state Small signal gain G1 = 35 I _p1 = 150 mA; P _p1 = 18 mW (P _in = − _{45dBm) G2 = 35 I p2 =} 150mA; P p2 = 18mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = 18mW G1 = 35 I p1 = 320mA; P p1 = 36mW G2 = 35 I p2 = 0 mA; P _p2 = 0 mW I _p3 = 150 mA; P _p3 = 18 mW I _p4 = 150 mA; P _p4 = 18 mW Saturation signal gain G1 = 24 I _p1 = 150 mA; P _p1 = 18 mW (P _in = −15 dBm) G2 = 24 _{I p2 = 150mA; P p2 =} 18mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = 18mW G1 = 2 _{I p1 = 320mA; P p1 =} 36mW G2 = 24 I p2 = 0mA; P p2 = 0mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = noise level 18mW small signal <6 I _p1 = 150mA P _p1 = 18 mW (P _in = −45 dBm) I _p2 = 150 mA; P _p2 = 18 mW I _p3 = 150 mA; P _p3 = 18 mW I _p4 = 150 mA; P _p4 = 18 mW <6 I _p1 = 320 mA; P _p1 = 36 mW _{I p2 = 0mA; P p2 =} 0mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; noise level P _p4 = 18 mW saturation signal _{<6,5 I p1 = 150mA; P} p1 = 18mW (P in = - _{15dBm) I p2 = 150mA; P} p2 = 18mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = 18mW <6,5 I p1 = 32 _{mA; P p1 = 36mW I p2} = 0mA; P p2 = 0mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = 18mW

Table 3 Results of the system according to FIG. 6 in the degraded “hot standby” mode [dB] Laser pump state Small signal gain G1 = 35 I _p1 = 150 mA; P _p1 = 18 mW (P _in = − _{45dBm) G2 = 35 I p2 =} 150mA; P p2 = 18mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = 18mW G1 = 34 I p1 = 150mA; P p1 = 18mW G2 = 34 I p2 = 0 mA; P _p2 = 0 mW I _p3 = 150 mA; P _p3 = 18 mW I _p4 = 150 mA; P _p4 = 18 mW Saturation signal gain G1 = 24 I _p1 = 150 mA; P _p1 = 18 mW (P _in = −15 dBm) G2 = 24 _{I p2 = 150mA; P p2 =} 18mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = 18mW G1 = 22 _{5 I p1 = 150mA; P p1} = 18mW G2 = 22,5 I p2 = 0mA; P p2 = 0mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = noise level 18mW small signal <6 I _{p1 = 150mA; P p1 = 18mW} (P in = -45dBm) I p2 = 150mA; P p2 = 18mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = 18mW <6,5 I p1 = 150mA _{; P p1 = 18mW I p2 =} 0mA; P p2 = 0mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; noise level P _p4 = 18 mW saturation signal _{<6,5 I p1 = 150mA; P} p1 = 18mW _{(P in = -15dBm) I p2} = 150mA; P p2 = 18mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = 18mW <7 I p1 _{150mA; P p1 = 18mW I p2} = 0mA; P p2 = 0mW I p3 = 150mA; P p3 = 18mW I p4 = 150mA; P p4 = 18mW

Table 4 Results of the system according to FIG. 8 in the “hot standby” mode with reduced performance [dB] Laser pump state Small signal gain G = 35 I _p1 = 150 mA; P _p1 = 18 mW (P _in = − 45 dBm) I _p2 = 150 mA; P _p2 = 18 mW G = 30 I _p1 = 150 mA; P _p1 = 18 mW I _p2 = 0 mA; P _p2 = 0 mW Gain of saturation signal G = 24 I _p1 = 150 mA; P _p1 = 18 mW (P _in = −15 dBm) I _p2 = 150 mA; P _p2 = 18 mW G = 20 I _p1 = 150 mA; P _p1 = 18 mW I _p2 = 0 mA; P _p2 = 0 mW Small signal noise value <6 I _p1 = 150 mA; P _p1 = 18 mW (P _in = −45 dBm) I _p2 = 150 mA; P _p2 = 18 mW <7 I _p1 = 150 mA; P _p1 = 18 mW I _p2 = 0 mA; P _p2 = 0 m Noise level W saturation signal _{<6,5 I p1 = 150mA; P} p1 = 18mW (P in = -15dBm) I p2 = 150mA; P p2 = 18mW <8 I p1 = 150mA; P p1 = 18mW I p2 = 0mA ; P _p2 = 0 mW

Table 5 Results of the system according to FIG. 8 in the “hot standby” mode with no performance degradation [dB] Laser pump state Small signal gain G = 35 I _p1 = 150 mA; P _p1 = 18 mW (P _in = − 45 dBm) I _p2 = 150 mA; P _p2 = 18 mW G = 35 I _p1 = 320 mA; P _p1 = 36 mW I _p2 = 0 mA; P _p2 = 0 mW Gain of saturation signal G = 24 I _p1 = 150 mA; P _p1 = 18 mW (P _in = −15 dBm) I _p2 = 150 mA; P _p2 = 18 mW G = 24 I _p1 = 320 mA; P _p1 = 36 mW I _p2 = 0 mA; P _p2 = 0 mW Small signal noise value <6 I _p1 = 150 mA; P _p1 = 18 mW (P _in = −45 dBm) I _p2 = 150 mA; P _p2 = 18 mW <6 I _p1 = 320 mA; P _p1 = 36 mW I _p2 = 0 mA; P _p2 = 0 noise level mW saturation signal _{<6,5 I p1 = 150mA; P} p1 = 18mW (P in = -15dBm) I p2 = 150mA; P p2 = 18mW <6,5 I p1 = 320mA; P p1 = 36mW I p2 = 0 mA; P _p2 = 0 mW

[Brief description of the drawings]

FIG. 1 is a diagram of a possible optical amplification system comprising a two-stage amplifier.

FIG. 2 is a diagram of an optical amplification system according to the first embodiment of the present invention.

FIG. 3 is a diagram of one preferred embodiment of an optical amplification system of the type shown in FIG.

FIG. 4 is a diagram of an optical amplification system according to a second embodiment of the present invention.

FIG. 5 is a diagram of an optical amplification system according to a third embodiment of the present invention.

6 is a diagram of one preferred embodiment of an optical amplification system of the type shown in FIG.

FIG. 7 is a schematic diagram of an optical communication system according to the present invention.

FIG. 8 is a diagram of a conventional optical communication system according to US Pat. No. 5,173,957.

[Explanation of symbols]

802 First optical fiber line 804 Second optical fiber line 806, 808 Amplifying fiber for first optical fiber 810, 812 Amplifying fiber for second optical fiber 814, 816, 818, 820 Laser pump 822, 824 , 826,828 Coupler 830,832,834,836 WDM

 ──────────────────────────────────────────────────の Continuation of front page (71) Applicant 591011856 Pirelli Cavies System e. p. A (72) Inventor Paolo Ottolengi F-Fr.

Claims (18)

[Claims] 1. An optical fiber line, a first transmitter transmitting at least one signal over a first optical fiber line, and a second transmitter transmitting at least one signal over a second optical fiber line. A at least one two-stage amplifier in each of the first and second lines, and a laser pump for providing an excitation signal to each of the stages of the amplifier;
A first receiver that receives a signal from a first optical communication line, and a second receiver that receives a signal from a second optical communication line, an optical communication system with improved reliability, wherein the first and An optical communication system wherein the laser pump forms a single system for providing a first excitation signal to at least one stage of at least one amplifier in each of the second lines. 2. The optical communication system according to claim 1, further comprising providing a second excitation signal to another stage of at least one amplifier of each of the first and second lines. . 3. The optical communication system according to claim 1, wherein at least four laser pumps are provided. 4. The optical communication system according to claim 1, wherein the laser pump is a laser diode pump. 5. The optical communication system according to claim 3, wherein the first coupler couples the output signals of the first and second laser pumps, and the output signals of the third and fourth laser pumps. And a second coupler that couples
Optical communication system. 6. The optical communication system according to claim 5, wherein a third combined signal from the first coupler and the first combined signal from the second coupler. The optical communication system further comprising: a coupler; and a fourth coupler that combines the second combined signal from the first coupler and the second combined signal from the second coupler. 7. The optical communication system according to claim 1, wherein each of the stages of the amplifier in the first and second lines is connected to a wavelength division multiplexer. Optical communication system. 8. The optical communication system according to claim 1, wherein said at least one of each of said first and second lines is provided.
An optical communication system, wherein the two two-stage amplifiers further comprise an insulator disposed between each stage of the first and second amplifiers. 9. An improved optical amplification system comprising two fiber optic lines, at least one two-stage amplifier in each line, and a laser pump for providing an excitation signal to said stage of said amplifier. An optical amplification system wherein the laser pump forms a single system for providing a first excitation signal to at least one stage of the at least one amplifier in each of the first and second lines. 10. The optical amplification system according to claim 9, further comprising: providing a second excitation signal to another stage of the at least one amplifier in each of the first and second lines. system. 11. The optical amplification system according to claim 9, wherein there are at least four laser pumps. 12. The optical amplification system according to claim 9, wherein the laser pump is a laser diode pump. 13. The optical amplification system according to claim 11, wherein a first coupler that combines output signals of the first and second laser pumps and an output signal of the third and fourth laser pumps are used. An optical amplification system, further comprising a second coupler for coupling. 14. The optical amplification system according to claim 13, wherein a third combined signal from the first coupler and the first combined signal from the second coupler. The optical amplification system further comprising: a coupler; and a fourth coupler that combines the second combined signal from the first coupler and the second combined signal from the second coupler. 15. The optical amplification system according to claim 9, wherein each of the stages of the amplifier in the first and second lines is connected to a wavelength division multiplexer. system. 16. The optical amplification system according to claim 9, wherein at least one two-stage amplifier in each of the first and second lines comprises a stage of the first and second amplifiers. An optical amplification system further comprising an insulator disposed therebetween. 17. A method for providing a laser pump signal in an optical communication system comprising first and second optical fiber lines, comprising: a) generating first and second laser pump signals; b. D.) Combining the first and second laser pump signals so as to form first and second output signals; c) generating third and fourth laser pump signals; Combining the third and fourth laser pump signals to form third and fourth output signals. 1) The first of the first fiber optic line amplifiers. And one of the second stages and to one of the first and second stages of the amplifier of the second fiber optic line are provided with first and second output signals; The first and second of the first optical fiber line amplifier A method wherein third and fourth output signals are provided to the other of the stages and to the other of the first and second stages of the second fiber optic line amplifier. 18. The method according to claim 17, wherein the first and third output signals are combined to form fifth and sixth output signals, while the second and fourth output signals are formed. Are coupled to form seventh and eighth output signals, wherein each of the fifth, sixth, seventh, and eighth output signals is a single amplifier of the second fiber optic line amplifier. The method, which is supplied to the stage.