KR20010050710A - Optical amplifying unit and optical transmission system - Google Patents

Abstract

PURPOSE: An optical amplifying unit and an optical transmission system are provided to reduce the loss of signal by applying pump radiation to an active fiber and to be suitable for a WDM transmission system. CONSTITUTION: The optical amplifying unit includes an input(101) for the input of optical signals, an output(102) for the output of the optical signals, a single-mode active fiber(103) doped with Er and Yb, optically connected to the input and the output, and adapted to amplify the optical signals, a first pump source(104) for generating a first pump radiation including an excitation wavelength for Er, a second pump source(106) for generating a second pump radiation including an excitation wavelength for Yb, a first optical coupler(105) for optically coupling the first pump radiation into the core of the active fiber in a co-propagating direction with respect to signal direction, and a second optical coupler(107) for optically coupling the second pump radiation into the core of the active fiber in a counter-propagating direction with respect to signal direction.

Description

OPTICAL AMPLIFYING UNIT AND OPTICAL TRANSMISSION SYSTEM

It is an object of the present invention to provide an optical amplifier for use in optical communications. The present invention relates to an optical transmission system, and more particularly, to a wavelength division multiplexing (WDM) optical transmission system using the optical amplifier. The optical amplifier of the present invention is also suitable for use with analog CATV systems.

In a WDM optical transmission system, an optical signal including several optical channels is transmitted by wavelength division multiplexing through the same line, and includes one or more optical amplifiers. Fiber channels can be digital or analog and are distinguishable because each is combined to a specific wavelength.

Currently, long distance high-capacity optical transmission systems do not require OE / EO conversion using optical fiber amplifiers that are different from conventional electronic regenerators. The optical fiber amplifier includes an optical fiber of a predetermined length and has a shim doped with one ion of rare earth oxide to amplify the optical signal by induced emission when excited by pump radiation. When inserted into active fibers, the pump spinning excites ions from certain raretoelements, allowing the seam to obtain information about the signals that carry signals along the fibers.

Rare earth elements used for doping generally include erbium (Er), neodymium (Nd), ytterbium (Yb), samarium (Sm), thulium (Tm), praseodymium (Pr). The particular rare earth element or element used is determined in accordance with the wavelength of the pump light and the wavelength of the input signal light. For example, erbium is used for input signal light having a wavelength of 1.55 mu m and pump power having a wavelength of 1.48 to 0.98 mu m. Doping erbium and ytterbium ions simultaneously allows a wider range of pump wavelength bands to be used.

Erbium-doped optical fibers have been used in both optical amplifiers and lasers. The operating wavelength is very important because it matches the third window for optical fiber communication around 1550 nm. Applicant's European Patent Application No. 98110594.3 discloses a 32 channel WDM optical fiber system using erbium doped fiber amplifiers (EDFAs) in the wavelength bands 1529-1535 nm and 1541-1561 nm.

Several methods, such as amplification gain and amplification bandwidth, have been proposed to improve system performance.

One method for improving system performance consists of co-doping erbium doped amplified fibers with ytterbium (Yb). Doping active fibers with erbium and ytterbium not only extends the pump absorption band from 800 nm to 1100 nm while providing flexibility in the choice of pump wavelength, but also increases the ground state absorption rate due to the high absorption means and the dopant solubility of ytterbium. Let's do it. Ytterbium ions absorb most of the pump light, and subsequent cross relaxation between the erbium and the adjacent ions of ytterbium causes the energy absorbed in the erbium system to be transferred. "+24.6 dBm output power Er / Yb co-doped optical amplifiers pumped by diode-pumped Nd: YLF lasers" (Grove et al., Pages 1275-1276 of Electronics Letters 1992, 28 (13)) and "Diode-pumped Nd 1.56 μm Yb-sensitized Er fiber lasers pumped by YAG and Nd: YLF lasers (Maker, Pugson: Electronics Letters 1992, pages 1160-1161 of 1992, 24 (18)). It is applied to effectively excite fiber amplifiers and lasers through direct pumping in the long wavelength tail of absorption spectroscopy. This pumping is performed by a diode pumped solid state laser such as a 1047 nm Nd: YLF laser or a 1064 nm ND: YAG laser.

The use of erbium and ytterbium co-doped amplified fibers for amplifying communication signals is well illustrated in European Patent Application Nos. 0 803 944 A2 and US Pat. No. 5,225,925. European Application 0 803 944 A2 is for a multi-stage erbium-doped fiber amplifier (EDFA) operating in the 1544-1562 nm wavelength band and includes a first stage containing erbium and aluminum and other rare earth elements such as erbium and ytterbium. It consists of a second step. Such multi-stage EDFAs have excellent characteristics in the recited wavelength bands across all erbium amplification systems, for example, with relatively low noise profiles, relatively wide plate gain areas and relatively high output power. However, the applicant has noted that the amplifier of European application 0 803 944 A2 has no advantage in light of the number of channels transmitted. The amplification bandwidth is limited to a relatively narrow 1544-1562 nm band. The Er / Yb second stage is also pumped by a diode pumped Nd-doped fiber laser emitting at 1064 nm. This pump source is used for the excitation of mono-amplified fibers and is relatively expensive and bulky.

U. S. Patent No. 5,225, 925 relates to an optical fiber for amplifying or sourcing an optical signal in a single traversal mode. The optical fiber is composed of a host glass doped with erbium and a photosensitive agent such as ytterbium (Yb) or iron (Fe). Host glass is doped silica glass (doped with phosphate or borate). Applicants note that U. S. Patent No. 5,225, 925 makes the amplified fiber particularly suitable for transmission of 1535 nm single channel and not for WDM transmission due to the shape of the gain curve. In addition, such amplified fibers are suitable for being pumped by diode-pumped neodymium doped fiber lasers, including the disadvantages mentioned above, to excite ytterbium ions.

EP 0 803 944 A2 and U. S. Patent No. 5,225,925 both do not disclose amplification by Er / Yb co-doped optical amplifiers of signals in wavelength bands different from those in the vicinity of 1550 nm. .

An improved Er / Yb amplified fiber can be obtained by cladding pumping technology, which consists of pumping active fibers in the inner sheathing area surrounding the seam rather than directly pumping the seam. Cladding pumping is equipped with a high power broadstripe diode and a diode bar for a small area pump source, which is efficient and inexpensive for the double coated rare earth element single mode fiber. Output power from hundreds of milliwatts to collection watts is maintained by this technique. Double-coated Er / Yb fibers with diode arrays at 980 nm are "Er ³⁺ / Yb ³⁺ co-doped fiber lasers and diode-array pumping amplifiers" (Minelli, IEEE Photonics Technology Letters, 1993, 5, (3 (Pages 301-303). The erbium- ytterbium co-doped configuration provides higher ground state absorption for erbium in the 980 nm band than single-doped erbium fibers, resulting in a very short optimum length.

WO 95/10868 discloses a technique (samely described as an inner sheath or an outer shim) for inserting pump spinning into a portion of the fiber outside the shim. Here there is a fiber optical amplifier where the pump power provided by the multimode source is cross-connected to the outer core (equivalent to the inner coating) of the fiber through the multimode power and the multimode optocoupler. Pump power delivers through the outer core and interacts with the inner core to pump the active material contained in the inner core. This pump technique has been disclosed in US Pat. No. 5,291,501, a single mode optical fiber with a doped shim and a doped inner sheath.

Several ways of increasing the number of channels to be transmitted have been presented. One way to increase the number of channels is to narrow the channel spacing, but narrowing the channel spacing degrades nonlinear effects such as four-wave mixing or cross-phase modulation and requires precise wavelength control of the optical transmitter. For this reason, channel intervals below 50 GHz are virtually difficult to achieve.

Another way to increase the number of channels is to widen the available wavelength bandwidth in the low loss region of the fiber. Optical amplification in the wavelength region beyond the conventional 1550 nm transmission band is important. In particular, the high wavelength band around 1590 nm, especially between 1565 nm and 1620 nm, is a very promising band for long distance optical transmission in that a large number of channels can be allocated in the band. If an optical amplifier for the 1565-1620 nm band has to deal with a large number of channels, the spectral gain characteristics of such an amplifier are fundamental to maximizing the performance and cost of the system. The use of a transmission wavelength region around 1590 nm parallel to the 1530-1550 wavelength region of the erbium doped fiber amplifier is noticeable. An additional advantage of having a 1590 nm wavelength range is the use of distributed mobile fibers (DSF) for WDM transmission without degradation by four-wave mixing.

Some patent publications or other publications deal with amplification in high wavelength transmission bands from 1565 nm to 1620 nm, but all of these documents deal only with erbium-doped fiber amplifiers.

The following documents suggest several ways of extending the available bandwidth to the high wavelength transmission band.

U.S. Pat.No. 5,500,764 relates to SiO ₂ -Al ₂ O ₃ -GeO ₂ single mode optical fibers pumped by 1.55 μm and 1.47 μm light sources and doped with erbium suitable for amplifying optical signals between 1.57 μm and 1.61 μm. It has a length between 150 m and 200 m.

"Flat Gain Er ³⁺ -doped Fiber Amplifiers for WDM Signals in the 1.57-1.60 µm Wavelength Range" (Ono et al .: Vol. 9, No. 5, IEEE Photonics Technology Letters, May 1997, 596-599 Page) shows a flat-gain Er ³⁺ -doped silica-based fiber amplifier for 1.58 µm band WDM signals, but different fiber lengths have been tested and the authors have found that 200 m is EDF (erbium-doped fiber) for high-gain and low-noise EDFA configurations. ) Was the optimal length.

"Broadband, flat gain, erbium-doped fiber amplifiers with 3 dB bandwidth of> 50 nm" (Masd et al .: Electronics Letters, Vol. 33, No. 12, pages 1070-1072, June 5, 1997) Two-stage erbium-doped fibers and intermediate equalizers are presented for the 52 nm band (1556-1608 nm) for the silicate erbium-doped fiber amplifiers and the 50 nm band for the fluoride erbium-doped fiber amplifiers (1556-1604 nm). do. In addition, in the case of silicate erbium doped fiber amplifiers, the second stage includes 50 m EDF and 26 m EDF, respectively.

"Low PMD and Minor Multipass Interference Experiments in Ultra-Plated Wideband EDFAs Using Many Doped Erbium Fibers" and "Optical Amplifiers and Their Applications" (Jolley et al .: July 27-29, TuD21 / 124-127 The Colorado Bale Council has proposed a wideband EDFA that uses 45 m of erbium fiber to amplify the signal in the 1585 nm band, reaching a maximum external power of 1570 to +18.3 dBm or more.

Applicant amplifies a conventional line EDFA suitable for amplifying an optical signal at high wavelength bands with an optical signal having a total input power of approximately -10 dBm up to a maximum power value of 19 dBm or less (ie, with a maximum gain of approximately 29 dB). It was observed that it can be made. The total input power of approximately -10 dBm is generally a good reference value for optical transmitters in long distance transmission systems. Low input power is not proposed. Although EDFA has a higher gain for low power input signals than for high power input signals, in this case ASE (amplified instantaneous emission) increases to a value where the signal for the noise ratio becomes very low. Conversely, signal input powers exceeding -10 dBm, for example up to a loss of transmission fiber length, tend to saturate the gain resulting in energy loss. Optical transmission systems using EDFA and 64 channels between 1575 nm and 1602 nm provide 0.2 dBm maximum power per channel at the output of the EDFA line and virtually limit the maximum span length to less than 100 km.

Applicants have found that for Erbium-doped active fibers of a certain length, the gain curve versus erbium concentration increases and decreases to a maximum corresponding to the optimum value of the erbium concentration. A high gain can be obtained by increasing the length of the active region doped with erbium, i.e. by increasing the active fiber length. Conventional long-range WDM optical transmission systems for high wavelength bands using erbium doped active fibers require fiber lengths of several hundred meters to reach relative high gains. At present, certain erbium-doped active fibers with a large diameter seam are proposed, which allows for relatively high gains with fiber lengths of up to 30-40 m.

Applicants have also found that transmission systems comprising erbium- ytterbium co-doped amplifiers in the 1565-1620 nm band provide a high degree of performance. In particular, high performance is provided for optical amplifiers doped only with erbium. Applicant's European Patent Application No. 98117898 (filed Sep. 22, 1998) discloses erbium-ytterbium co-doped in a single stage configuration (bidirectional pumping) or in a double stage configuration (bidirectional pumping or co-transmission pumping). An optical amplifier comprising two erbium- ytterbium co-doped fiber amplifiers has been proposed providing high amplification in the 1575-1602 nm wavelength range. Amplifiers proposed to achieve very high power gains include erbium doped fiber preamplifiers and one or more double coated erbium- ytterbium co-doped fiber amplifiers. Double-coated active fibers have a high pump performance while taking advantage of the multimode pumping structure. The pump laser used was a multimode wide area laser with an emission wavelength in the 920-980 nm wavelength range. At 920 nm each laser is suitable for providing about 400 mW of pump power to the active fiber.

In this amplifier, the Applicant has found that the implementation of a WDM coupler suitable for combining multimode pump radiation into double coated fibers is important. Coupling multimode pump spinning into double coated fibers is accomplished by microoptical (glass type) WDM couplers, which have a much higher coupling effect than fused fiber WDM couplers. The WDM coupler must be able to combine the pump radiation (in the range 920-980 nm) and the transmitted signal (in the range 1575-1602 nm) in the shim to the inner sheath of the fiber. Therefore, the coupler must have an optical characteristic to allow a predetermined light space distribution in addition to the required wavelength selectivity. If a microoptical coupler is used, a focusing lens system that can provide space distribution of light is very difficult to install. Therefore, the use of the double-coated active fiber is difficult to increase the coupling effect between the pump source and the active fiber. In addition, the microoptic coupler considered has a relatively high insertion loss of more than 1dB at 1550 nm.

The present invention provides an advantage overcoming strain amplifier arrangements and well known amplification elements suitable for use in the 1565-1620 nm band. The proposed amplifier is a booster amplifier, especially suitable for use in WDM transmission system.

A single-mode and single-coated active fiber co-doped with erbium and ytterbium by a first pump source suitable for exciting erbium by a first pump spinning and a second pump source suitable for exciting ytterbium by a second pump spinning By pumping a compact amplifier with high performance is achieved.

The first pump spinning includes wavelengths between 1465 nm and 1495 nm and is supplied to the active fiber in the co-transfer direction (for the transmitted signal), and the second pump spinning includes wavelengths between 1000 nm and 1100 nm ( For the transmitted signal) is supplied to the active fiber in the direction of reversal moon.

The first pump source is coupled to the active fiber by a microoptical WDM coupler and the second pump source is coupled to the active fiber by a fused fiber WDM coupler.

The amplifier of the present invention extends the range of the input signal to low power for a general booster. For example, this feature is a transmission system that includes a device with minimal loss, for example an optical add / drop multiplexer (OADM), (i.e., a device that inserts and extracts optical signals into the system) or an amplifier. It is a dispersion compensator that goes back to. These additional losses are in fact acceptable without significantly reducing amplification.

Another advantage of the present invention is to provide pump spinning to the active fiber using a single mode coupler, which reduces signal loss.

In addition, the amplifier of the present invention extends beyond 1565 nm and has a relatively wide wavelength amplifier band, which is particularly suitable for use in a WDM transmission system.

1 is a block diagram of an optical transmission system of the present invention.

2 is a graph of the spectral gain characteristics of the optical transmission system of FIG. 1 by designating signal transmission bands BB, RB1, and RB2.

3 is a detailed view of the optical transmission system multiplexing unit of FIG.

4 is a detailed view of the transmitter power amplifier of the optical transmission system of FIG.

FIG. 5 is a graph showing a filter implementation form of a de-emphasis filter for the optical transmission system of FIG. 1. FIG.

6 is a detailed view of the intermediate station of the optical transmission system of FIG.

7 is a detailed view of the optical transmission system receiver preamplifier of FIG.

8 is a detailed view of the optical transmission system multiplexing unit of FIG.

9 is a view showing the configuration of an optical amplifier according to the present invention;

FIG. 10 is a configuration diagram illustrating a pump source included in the optical amplifier of FIG. 9. FIG.

11A and 11B are diagrams showing the configuration of a multi-mode pump operation of a double coated fiber and a double coated fiber used as a pump source of FIG.

12 is a lattice recording assembly used to record the lattice in the double coated fiber of the pump source of FIG.

Figure 13 is a response curve of the fiber laser used for the experimental measurement.

14 and 15 are the experimental results obtained with the amplifier according to the present invention.

16 and 17 are flux diagrams of a method for recording a lattice in active fibers used in the pump source of FIG.

18A and 18B are diagrams showing predetermined parameter changes during the lattice writing process according to the methods of Figs. 16 and 17;

19 to 21 are simulation execution diagrams of the fiber laser used in the pump source of FIG.

According to a first aspect of the present invention there is provided an optical link for transmitting an optical signal, an optical receiver for receiving the optical signal, and an optical fiber link suitable for transferring the optical signal and optically coupling the transmitter to the receiver. And an optical amplifier adapted to amplify the optical signal and coupled along the link, the optical amplifier comprising an input for input of the optical signal, an output for output of the optical signal; Active fiber having a first end optically coupled to the input and a second end optically coupled to the output to amplify the optical signal, co-doped with erbium / ytterbium, a first pump radiation and a second pump radiation A first optocoupler and an optocoupler for optically coupling the first and second pump sources to the active fiber; Consisting of two optocouplers, the first pump radiation comprising an excitation wavelength for erbium and the second pump radiation comprising an excitation wavelength for ytterbium.

The optical amplifier has a wavelength amplification band of 1565 nm or more.

The first optical coupler is optically coupled to the first end of the active fiber in order to supply the first pump radiation to the active fiber in the co-transfer direction with respect to the optical signal, and the second optical coupler is in the reverse transverse direction with respect to the optical signal It is optically coupled to the second end of the active fiber to supply a second pump spinning to the active fiber.

Active fibers are single coated fibers and monomodal fibers.

The first pump spinning has a wavelength between 1465 nm and 1495 nm and the second pump spinning has a wavelength between 1000 nm and 1100 nm.

The first optocoupler is a microoptical WDM coupler and the second optocoupler is a fused fiber WDM coupler.

According to a second aspect of the present invention, the present invention comprises the steps of supplying an optical signal to an erbium / ytterbium co-doped active fiber and optically pumping the active fiber during the optical signal supply step, wherein the optical pumping step is performed by erbium And a method for amplifying a signal comprising supplying said active fiber with a first pump spinning for exciting the metal and a second pump spinning for exciting the ytterbium.

The step of supplying the first pump radiation includes supplying the first pump radiation to the active fiber in the direction of co-transmission for the optical signal, and the step of supplying the second pump radiation in the reverse moon direction for the optical signal Supplying the second pump spinning to the active fibers.

The step of supplying the first pump spinning to the active fiber includes supplying the active fiber with excitation of erbium having a wavelength between 1465 nm and 1495 nm.

The step of supplying the second pump spinning to the active fiber comprises supplying the active fiber excitation radiation for ytterbium having a wavelength between 1000 nm and 1100 nm.

The active fiber includes a core and a sheath, and in the step of supplying the first pump spinning and the second pump spinning to the active fiber, the first pump spinning and the second pump spinning include feeding the core of the active fiber. do.

The step of supplying the optical signal to the active fiber comprises supplying an optical signal having a wavelength of 1565 nm or more to the active fiber.

According to a third aspect of the present invention, an optical amplifier of the present invention comprises an input for input of an optical signal, an output for outputting the optical signal, and erbium / ytterbium co-doped and optically connected to the input and output. An active fiber suitable for amplifying a signal, a first pump source and a second pump source for generating a first pump radiation and a second pump radiation, respectively, and the first pump source and a second pump source respectively. A first optocoupler and a second optocoupler for photocoupling to said first pump radiation comprising an excitation wavelength for erbium and said second pump radiation comprising an excitation wavelength for ytterbium.

The excitation wavelength for erbium is between 1465 nm and 1495 nm and the excitation wavelength for ytterbium is between 1000 nm and 1100 nm.

The first optical coupler is connected between the input and the active fiber to supply a first pump radiation to the active fiber in the co-transfer direction with respect to the optical signal, and the second optical coupler is a second pump radiation against the optical signal. Is connected between the output and the active fiber in order to supply the active fiber in the direction of reversal.

The active fibers are single coat and single mode fibers.

The first optocoupler is a microoptical WDM coupler and the second optocoupler is a fused fiber WDM coupler.

The second pump source comprises an active fiber and a fiber laser suitable for generating a second pump spinning, and a pump laser source suitable for pumping the active fiber.

The active fiber includes a double coated fiber. The active fiber also includes an optical fiber doped with Yb.

The fiber laser includes a first Bragg grating and a second Bragg grating recorded at both ends of the active fiber. The pump laser source is a light area laser diode.

DETAILED DESCRIPTION The following detailed description is merely illustrative and does not limit the invention, and the examples and the following description of the present invention present the advantages and objects of the present invention.

Referring to FIG. 1, the optical transmission system 1 includes an optical fiber line 30 connecting a first terminal site 10, a second terminal site 20, two terminal sites 10, 20, and an optical fiber line. One or more line sights 40 along terminal 30 between terminal sites 10 and 20.

The optical transmission system 1 is unidirectional. The signal transmission system 1 is a unidirectional signal for a signal traveling from one terminal site to another terminal site (in this case, from the first terminal site to the second terminal site) or for a bidirectional system in which the signal travels in both directions. Valid. In addition, although the optical transmission system 1 can transmit up to 128 channels, the number of channels is not a feature limiting the spirit and scope of the present invention, and approximately 128 channels can be used according to the demands and requirements of a specific optical transmission system. Is there.

The first terminal site 10 includes a multiplexing unit (MUX) 11 and a transmission power amplifier unit (TPA) 12 suitable for receiving a plurality of input channels 16. The second terminal site 20 includes a receiver amplifier (RPA) and a demultiplexer (DMUX) 15 suitable for outputting a plurality of output channels 17.

Although the multiplex unit 11 may classify about three input channels 16 into subbands, the multiplex unit 11 of FIG. 3 may convert the input channel 16 into a blue band BB and a first red band. It is multiplexed or grouped into three subbands such as the band RB1 and the second red band RB2.

Three subbands BB, RB1, RB2 are received after the TPA section 12 as a separate subband or as a combined wideband. The optical fiber line 30 portion is adjacent to one or more line sights 40 having a TPA portion 12, and to the RPA portion 14 and other line sights 40 (not shown). The TPA unit 12 receives, amplifies, and maximizes separate subbands BB, RB1, and RB2 from the multiplexing unit 11 and utilizes a single wideband (SWB) for transmission to the first portion of the optical fiber line 30. To (FIG. 4). Linesight 40 receives a single wideband (SWB) and subdivides into three subbands (BB, RB1, RB2), adds or attenuates the signals in each of the three subbands (BB, RB1, RB2). The three subbands (BB, RB1, and RB2) are amplified, fully utilized, and recombined into a single wideband (SWB). To add or attenuate the operation, the line sight 40 is provided in the known type of increase / decrease optical multiplexer (OADM) or in the Applicant's European Patent Application No. 98110594.3.

The second portion of the optical fiber line 30 couples the output of the line sight 40 to the other line sight 40 (not shown) or to the RPA portion 14 of the second terminal site 20. The RPA unit 14 also takes full advantage of the single wideband SWB and divides the single wideband SWB into three subbands BB, RB1 and RB2 before outputting (Fig. 7).

The demultiplex unit 15 receives three subbands BB, RB1 and RB2 from the RPA unit 14 and divides the three subbands BB, RB1 and RB2 into respective wavelengths of the output channel 17. (FIG. 8). Some channels are reduced and / or increased at line sight 40, so the number of input channels 16 and output channels 17 is not equal.

For each subband BB, RB1, RB2, an optical link is defined between the corresponding input of the TPA section 12 and the corresponding output of the RPA section 14.

2 is a graph of the spectral emission range of an amplifier used in the optical transmission system 1 and corresponding to different gains and different allocations of the three subbands BB, RB1 and RB2 for the channel of the signal traveling through the fiber link. . In particular, the first subband BB comprises a range between 1529 nm and 1535 nm, which corresponds to the first amplification wavelength range of the erbium-doped fiber amplifier and assigns up to 16 channels. The second subband RB1 is between 1541 nm and 1561 nm, and corresponds to the second amplification wavelength range of the erbium-doped fiber amplifier and is allocated up to 48 channels. The third subband RB2 is between 1575 nm and 1602 nm and corresponds to an amplification wavelength range of the erbium / ytterbium doped fiber amplifier and is allocated up to 64 channels. A gain spectrograph of an erbium / ytterbium doped fiber amplifier is assigned channels up to 1620 nm and down to 1565 nm, although the 1575-1602 nm range provides the best performance in light of amplification.

Channels adjacent to the 128 channel system have a constant spacing of 50 GHz. Other constant intervals may be used, but the frequency intervals are not the same to mitigate two-wave mixing.

While the BB band includes a steep gain response, the Erbium-amplified band has RB1 and RB2 bands with a gentle gain characteristic. In order to use the erbium-doped fiber spectral emission range in the BB band, the optical transmission system 1 uses equalization means to flatten the gain characteristics within that range. As a result, by separating the erbium-doped fiber spectral emission range of 1529-1602 nm into three subbands (BB, RB1, RB2), the optical transmission system 1 effectively reduces most of the erbium-doped fiber spectral emission ranges. Provides and provides for compact WDM.

Hereinafter, various modules of the present invention shown in Figure 1 will be described in detail.

3 is a detailed view of the first terminal site 10. The first terminal site 10 includes an optical line terminal part (OLTE) 41 and a wavelength converter part (WCS) 42 in addition to the multiplex part 11 and the TPA part 12 (not shown).

The OLTE 41 corresponds to a standard line terminal device used in a standard system. For example, the amount of transmission / reception (TX /) equal to the number of channels in the WDM system 10 such as a SONET, ATM, IP, or SDH system. RX) portion (not shown). In one embodiment of the invention, OLTE 41 has 18 transmit / receive units. In the multiplex section 11, the OLTE 41 transmits a plurality of signals at a comprehensive wavelength. In the exemplary embodiment of FIG. 3, the OLTE 41 outputs a first 16 channel group, a second 48 channel group, and a third 64 channel group. However, as described above, the number of channels may vary depending on the needs and requirements of a particular optical transmission system.

For those of ordinary skill in the art, the OLTE 41 consists of a group of separate small OLTEs (e.g. three) that feed the information frequency to the WCS 22. Therefore, the WCS 42 includes 128 wavelength converter modules WCM1-WCM 128.

The WCM1-WCM16 sections each receive one of the first signal groups emitted from the OLTE 41, the WCM17-WCM64 sections each receive one of the second signal groups emitted from the OLTE 41, and the WCM65-WCM128 sections each receive the OLTE 41. Receive one of the third group of signals emitted from < RTI ID = 0.0 > Each part converts the signal from the generic wavelength to the selected wavelength and retransmits it. Examples are OC-48 and STM-16 for receiving and retransmitting signals in a standard format, but the preferred operation of WCM1-128 is evident in the particular data format provided.

Each WCM1-128 includes a module having a photodiode (not shown) for receiving an optical signal from the OLTE 41 and converting it into an electrical signal, a laser or light source (not shown) for generating a fixed carrier wavelength, and an electrical signal. It consists of an electro-optic modulator such as a Mac-Zehnder modulator (not shown) for externally modulating the carrier wavelength. Alternatively, each WCM1-128 consists of a photodiode (not shown) with a laser diode (not shown) directly modulated with an electrical signal to convert the wavelength received at the carrier wavelength of the laser diode. In another variation, each WCM1-128 is a direct modulated or externally modulated laser with a module having a high sensitivity receiver (according to SDH or SONET standards) for receiving optical signals from trunk fiber line ends and converting them into electrical signals. It is composed of circles. By this modification, signal generation from the output of the trunk fiber line and transmission in the optical communication system are possible, which extends the total link length.

3 shows that the signal is provided and generated by the combination of OLTE 41 and WCM1-WCM128, but the signal is nevertheless provided and generated directly by the source, without being limited to its source.

The multiplex section 11 includes three wavelength multiplexers (WMs) 43, 44, and 45. For a 128 channel system, each selected wavelength signal output from WCM1-WCM16 is received by WM 43, and each selected wavelength signal output from WCM17-WCM64 is received by WM 44, and from WCM65-WCM128. Each selected wavelength signal output is received by the WM 45. The WMs 43, 44, and 45 combine the received signals of the three bands BB, RB1 and RB2 into three wavelength division multiplex signals, respectively. 3, WM 43 is a 16 channel wavelength multiplexer, such as a conventional 1x16 planar optical splitter, and WM 44 is a 48 channel wavelength multiplexer, such as a conventional 1x64 planar optical splitter with 16 unused ports. WM 45 is a 64 channel wavelength multiplexer, such as a conventional 1x64 planar optical splitter. Each wavelength multiplexer includes a second port (2x16 and 2x64 splitters) for providing an optical monitoring channel (not shown) to the optical transmission system 1. Of course, the WMs 43, 44, 45 may have more inputs than are used by the system to provide the space needed for system growth. For example, wavelength multiplexers using silica-on-silicon (SiO ₂ -Si) or silica-on-silica (SiO ₂ -SiO ₂ ) techniques are readily available to those of ordinary skill in the art. For WM, other techniques for reducing insertion loss are also applicable. Examples are array waveguide gratings (AWGs), cascade genders, fiber gratings, and interference filters.

4, the bands BB, RB1, and RB2 output from the multiplex section 11 are received by the TPA section 12. As shown in FIG. The band BB, RB1, RB2 signals are provided to the TPA section 12 from sources other than the OLTE 41, WCS 42, WM 43, 44, 45 configurations of FIG. For example, the band BB, RB1, RB2 signals are generated and supplied directly to the TPA section 12 without departing from the spirit of the invention.

The TPA unit 12 includes three amplifier units 51, 52, and 53, a coupling filter 54, and an equalization filter 61 for each of the bands BB, RB1, and RB2. The amplifier section 53 of the present invention is an erbium / ytterbium doped fiber amplifier, and the amplifier sections 51, 52 are preferably erbium doped two-stage fiber amplifiers (even if other rare earth oxide doped fiber amplifiers are used). (FIG. 9).

The outputs of amplifiers 51, 52, 53 are received by filter 54, which combines bands BB, RB1, RB2 into a single wideband SWB.

Each amplifier 51, 52 provides optical gain to a signal that is pumped and amplified by one or two laser diodes. The characteristics of each amplifier, including its length and pump wavelength, are chosen to make the best use of the amplifier's performance for the particular subband it is amplifying. For example, the first stage (preamplifier) of the amplifier sections 51 and 52 is pumped to a laser diode (not shown) operating at 980 nm for amplifying the BB and RB1 bands in linear or saturation schemes, respectively. Suitable laser diodes are available from the applicant. The laser diode is coupled to the optical path of the preamplifier using a 980/1550 WDM coupler (not shown) commonly available on the market. An example is SWDM0915SPR from Etec Dynamics in Rundy Avenue, 1885, San Jose, California. The 980 nm laser diode is quiet for amplifiers compared to other possible pump wavelengths.

The second stage of each amplifier section 51-53 operates in saturation. The second stage of the amplifier section 51 is erbium doped and amplifies the BB band with another 980 nm pump (not shown) coupled to the optical path of the WDM coupler (not shown). The 980 nm pump provides better gain and noise profile for signals in the low band covering 1529-35 nm. The second stage of the amplifier section 52 amplifies the RB1 band with a erbium-doped laser diode pump source operating at 1480 nm. Such a laser diode is JD Fidel's model FOL1402PAX-1, based in Neffen Heston Drive 570, Ontario, Canada. The 1480 nm pump provides better saturation conversion efficiency, which is used in the RB1 band for a large number of channels in the region covering 1542-61 nm. Alternatively, a high power 980 nm pump laser or a multiplexed pump source in the 980 nm wavelength range is used. Section 53 is described in detail with reference to FIG. 9.

A filter 61 is located in the RB1 band amplifier chain to equalize the signal level and SNRs at the system output over the RB1 band. In particular, the filter 61 is composed of a de-emphasis filter that attenuates the high-amplification wavelength region in the RB1 band. In use, the de-emphasis filter may be a split beam fore filter or the like having long-term Bragg grating technology. For example, a de-emphasis filter has an operating wavelength range of 1541-1561 nm and a peak transmission wavelength at 1541-1542 nm and 1559-1560 nm with relatively low and constant transmission for the wavelengths between these peaks. to be. 5 shows the filter shape or relative attenuation performance of the de-emphasis filter 61. 5 shows that the de-emphasis filter 61 has areas of peak transmission between 1542 nm and 1560 nm and a constant or flat attenuation area between 1546 nm and 1556 nm. The de-emphasis filter 61 for erbium doped fiber amplifiers only needs to add attenuation of about 3-4 dB at the wavelength between the peaks to smooth the gain response over the high band. The de-emphasis filter 61 has attenuation different from that of FIG. 5 depending on the gain-flatness requirements of the actual system provided (such as the dopant used in the fiber amplifier or the wavelength of the pump source for such an amplifier).

Alternatively, the de-emphasis filter 61 is omitted and the de-emphasis operation is obtained at the multiplex section 11 of the first terminal site 10 by attenuation.

After passing through the amplifier of the TPA 12, the respective amplification (BB, RB1, RB2) bands output from the amplifier sections 51, 52, 53 are received by the filter 54. The filter 54 is a band combining filter, which combines two subinterfering three-port filters (not shown) (a first filter combining the RB1 band and the BB band, and a BB / RB1 band provided by the first filter into the RB2 band). Second filter).

An optical monitor (not shown) and insertion for a service line through a WDM 1480/1550 interference filter (not shown) at a wavelength different from the communication channel (eg 1480 nm) are added at the common port. The optical monitor detects the optical signal to ensure that there is no brake in the optical transmission system 1. Service line insertion provides access to the line service module, which handles telemetry of alarms, monitoring, data and execution monitoring, alarm control and maintenance, and voice frequency call lines through optical supervision channels.

The single wideband output from the filter 54 of the TPA section 12 passes through the length of the transmission fiber (not shown) of the optical fiber line 30, such as 100 kilometers, to attenuate the signal in the single wideband (SWB). Linesight 40 then receives and amplifies the signal within a single wideband (SWB). 6, line sight 40 has several amplifiers (AMP) 64-69, three filters 70-72, equalization filter (EQ) 74, three OADM stages 75-. 77).

The filter 70 receives a single wide band (SWB) and separates the RB2 band from the BB and RB1 bands. The BB band is equalized by the equalization filter 74 and received by the first OADM stage 75 where a predetermined signal is added or reduced and amplified by the amplifier 65. The RB1 band is already passed through the de-emphasis filter 61 in the TPA 12 which is first amplified by the amplifier 66 and received by a second OADM step 76 where a predetermined signal is added or reduced. 67). The RB2 band is first received by a third OADM stage 77 where amplified by the amplifier 68 and a predetermined signal is added or reduced, and amplified by the amplifier 69. The amplified BB, RB1, and RB2 bands are recombined into a single wide band (SWB) by the filter 72.

Amplifier 64 receives a single wideband (SWB), which consists of a single optical fiber amplifier operating in a linear scheme. That is, the amplifier 64 operates under the condition that its output power depends on the input power. According to practical implementation, the amplifier 64 is a single stage or a multi stage amplifier. By operating in linear conditions, the amplifier 64 ensures relative power independence between the BB and RB1 band channels. In other words, with amplifier 64 operating in linear conditions, the output power (and signal and noise ratio) of an independent channel in one of the two subbands (BB, RB1) is the channel in the other subbands (RB1, BB). If it is not added or removed, it does not change significantly. In order to achieve stiffness for some or all channels in a compact WDM system, a component such as amplifiers 64 and 68 in line sight 40 in a desaturation diagram is required before extracting a portion of the channel to separate equalization and amplification. The first stage amplifier must be operated. In one embodiment of the invention, the amplifiers 64 and 68 are erbium-doped fiber amplifiers pumped in a co-transfer direction in a laser diode (not shown) operating in a 980 nm pump to achieve a noise profile of less than 5.5 dB per band. to be.

The filter 71 is composed of, for example, a three-port element, an interference filter having a drop port for supplying the BB band to the equalization filter 74, and a reflection port for supplying the RB1 band to the amplifier 66.

Amplifier 66 is a single erbium-doped fiber amplifier that operates in saturation and whose output power is independent of the input power. Amplifier 66 adds the power boost to the channel in the RB1 band compared to the channel in the BB band. Since the number of channels in the RB1 band as compared to the BB band is as large as 48 channels in comparison with the 16 channels, the RB1 band channel has a low gain when passing through the amplifier 64. As a result, the amplifier 66 estimates the power for the channel in the RB1 band compared to the BB band. Of course, for other arrangements of channels between the BB band and the RB1 band, the amplifier 66 is not needed and may be necessary on the BB band side of the line sight 40.

For the RB1 band of the channel, amplifiers 64 and 66 act as two-stage amplifiers, with a first stage operating in linear mode and a second stage operating in saturation. The amplifiers 64, 66 are pumped to the same laser diode pump source to stabilize the output power between the channels in the RB1 band. In European patent application 695049, residual pump power from amplifier 64 is provided to amplifier 66. In detail, the line sight 40 includes a WDM coupler located between the amplifier 64 and the filter 71 to extract the 980 nm pump light remaining at the output of the amplifier 64. The WDM coupler could be model number SWDMCPR3PS110 from Etec Dynamics, 1885, Rundy Avenue, San Jose, California. The output from this WDM coupler is fed to a second WDM coupler of the same type and placed in the optical path after amplifier 66. The two couplers are met by the optical fiber 78 and transmit the remaining 980 nm pump signal with relatively little loss. The second WDM coupler passes the remaining 980 nm pump power through the amplifier 66 in the inverted direction.

The RB1 band signal from amplifier 66 is passed to an OADM stage 76 of known type or of the type disclosed in Applicant's European Patent Application No. 98110594.3. From OADM stage 76 the RB1 band signal is fed to amplifier 67. In an erbium-doped fiber amplifier, the amplifier 67 has a pump wavelength of, for example, 1480 nm from a laser diode source (not shown) with pump power that exceeds the laser (not shown) driving the amplifiers 64, 66. Get The pump wavelength of 1480 nm provides a good conversion effect with high output power compared to other pump wavelengths for erbium-doped fibers. A high power 980 nm pump source or group of multiplexed pumps, one at 976 nm, the other at 986 nm, or a bipolar multiplexed pump source at 980 nm is used to drive the amplifier 67. It is possible. Amplifier 67 operates at saturation to provide power boost for signals in the RB1 band, and is also configured as a multistage amplifier.

After passing through the amplifier 64 and the filter 71, the BB band enters the equalization filter 74. As described above, the gain characteristic of the erbium-doped fiber spectral emission range has a steep slope in the BB band region and a gentle slope in the RB1 band region. As a result, the channel in the BB band is amplified and amplified when the BB band or a single wideband (SWB including the BB band) is amplified by the erbium-doped fiber amplifier. In addition, when equalization means are applied to solve this problem of non-uniform amplification, equalization is applied over the entire spectrum of channels, resulting in continuous gain imbalance. However, if the spectrum of the channel is divided into the BB band and the RB1 band, equalization in the reduced operating range of the BB band smoothes the gain characteristics of the BB band channel.

The equalization filter 74 is composed of a two-port device based on a long term chirped Bragg grating technique that selectively attenuates at different wavelengths. For example, the equalization filter 74 for the BB band has an operating wavelength range of 1529 nm-1536 nm with a low wavelength below 1530.3 nm to 1530.7 nm. Equalization filter 74 is coupled separately to other filters (not shown) to provide gain equalization for the optimum filter shape and for the specific amplifiers used in WDM system 1 without being used separately. The equalization filter 74 may be manufactured or available by one of ordinary skill in the art. The specific structure used for the equalization filter 74 is within the scope of those skilled in the art and includes certain Bragg gratings, such as long term gratings, and interference filters or optical filters of the McGender type.

The BB band signal from the equalization filter 74 is passed to an OADM stage 75 of the same type as the OAMM stage 76 and to an amplifier 65. Like the erbium-doped fiber amplifier, the amplifier 65 is coupled to an optical path provided by a laser diode source (not shown) and coupled to an optical path that pumps to the amplifier 65 in a direction of inversion through a WDM coupler (not shown). It has a pump waveform. Since the channel in the BB band passes through the amplifier 64 and the amplifier 65, the equalization filter 74 compensates for gain imbalance by both amplifiers. The decibel drop for the equalization filter 74 should be determined according to the overall amplification and line power requirements for the BB band. The amplifier 65 operates in saturation to provide power boost to the signal in the BB band and is configured as a multi-stage amplifier.

The RB2 band is received from the fiber amplifier 68 and is an erbium dope fiber amplifier pumped with 980 nm or 1480 nm pump light, depending on system requirements. The RB2 band channel is passed from amplifier 68 to OADM stage 77 of the same type as OADM stages 75 and 76 and fed to amplifier 69. Amplifier 69 is an erbium / ytterbium co-doped amplifier suitable for amplifying the RB2 band (FIG. 10).

After passing through the amplifiers 65, 67 and 69, respectively, the amplified BB, RB1 and RB2 bands are recombined into a single wide band SWB by the filter 72. Like filter 54 of FIG. 4, filter 72 is provided by a first filter that combines two dependent interfering three-port filters (not shown), for example RB1 and BB bands, and a first filter. And a second filter for combining the BB / RB1 band into the RB2 band.

Like the TPA unit 12, the line sight 40 includes a service line insertion / extraction (not shown) and an optical monitor through a WDM 1480/1550 interference filter (not shown). One or more components are included at the midpoint of the line sight 40.

In addition to the amplifiers 64-69, filters 70-72 and 74, and the OADM stages 75-77, the line sight 40 performs dispersion compensation that occurs during the transmission of the signal along the long distance communication link to compensate for color dispersion. Module (DCM) (not shown). DCM (not shown) consists of various types of subunits that are top coupled with one or more amplifiers 65, 67, and 69 to compensate for the dispersion of channels in one or more of the BB, RB1, and RB2 bands. For example, DCM has an optical circulator with a first port connected to receive channels in three bands BB, RB1, RB2. The chirp Bragg grating is attached to the second port of the circulator. The channel exits the second port and reflects off the chirp Bragg grating to compensate for color dispersion. The distributed compensation signal exits the next port of the circulator for successive transmissions in the WDM system. In addition to the chirp Bragg grating, such as the length of the dispersion compensation fiber, other devices are used to compensate for color dispersion. The design and use of the DCM part does not limit the present invention, and the DCM part may be provided or omitted from the WDM system 1 depending on the overall requirements of the system configuration.

After the line sight 40, the combined single wideband (SWB) signal passes through the length of the long distance optical transmission fiber of the optical fiber line 30. If the distance between the first terminal site 10 and the second terminal site 20 is long enough to cause a reduction in the optical signal by more than 100 kilometers, one or more additional line sites 40 providing amplification are used. In a practical arrangement, five span (45 inches) of long-distance transmission fibers separated by four amplification line sights (40) are used, providing a length and 0.22 dB / km of total span loss of about 25 dB. Has power loss.

Following the final span of the transmission fiber, the RPA unit 14 receives a single wideband (SWB) from the last line sight 40 and prepares a single wideband (SWB) signal for reception and detection at the end of the communication link. Referring to FIG. 7, the RP unit 14 includes an amplifier (AMP) 81-85, filters 86 and 87, an equalization filter 88, and three router modules 91-93 if necessary. do.

Filter 86 receives a single wideband (SWB) and separates the RB2 band from the BB, RB1 bands. Amplifier 81 amplifies BB and RB1 bands to improve the signal-to-noise ratio for the channels doped with erbium and in the BB and RB1 bands. The amplifier 81 is pumped with a 980 nm pump or with a pump at a different wavelength to provide a lower noise figure for the amplifier. The BB and RB1 bands are in turn separated by the filter 87.

Like the TPA unit 12 and the line sight 40, the amplifiers 82 and 83 amplify the RB1 and BB bands by 980 nm pumping, respectively. In order to stabilize the output power between the channels in the RB1 band, the amplifiers 81 and 83 are pumped to the same 980 nm laser diode pump source using the optical fiber 89 which transmits the residual 980 nm pump signal with low loss. Specifically, amplifier 81 is coupled to a WDM coupler and is located between amplifier 81 and filter 87 to extract the 980 nm pump light remaining at the output of amplifier 81. As the WDM coupler, for example, the model number SWDMCPR3PS110 of Etec Dynamics, Rune Avenue 1885, San Jose, California, USA, is used. This output from this WDM coupler is fed to a second WDM coupler of the same type and located in the optical path after amplifier 83. The two couplers are met by the optical fiber 89 and transmit the remaining 980 nm pump signal with relatively little loss. The second WDM coupler passes the remaining 980 nm pump power through the amplifier 83 in the inverted direction. Therefore, the amplifiers 81-83, the filter 87, and the equalization filter 88 each have the same function as the amplifiers 64, 65, 67, the filter 71, and the equalization filter 74 of the line sight 40, respectively. And constitute identical or equivalent parts depending on the overall system requirements.

Amplifier 84 is coupled to filter 86 to receive and amplify the RB2 band. For example, amplifier 84 is an erbium doped amplifier, similar to amplifier 68 in FIG. The RB2 band channel is received by amplifier 85, which is a well-known type of erbium doped amplifier.

The RPA unit 14 is composed of a path step 90 for adapting the channel intervals within the BB, RB1, and RB2 bands to the channel separation capability of the demultiplex unit 15. In particular, if the channel in the WDM system 1 is for a tight interval (50 GHz) and the channel separation capability of the demultiplex unit 15 is for a wide channel interval (such as a 100 GHz grid), then the RPA unit 14 passes the path. Step 90 is included (FIG. 7). Other structures are added to the RPA unit 14 depending on the channel separation capability of the demultiplex unit 15.

The route step 90 includes three route modules 91-93. Each path module 91-93 separates each band into two subbands, each subband containing one half of the channel of the corresponding band. For example, if the BB band includes 16 channels (λ1-λ16) and each is separated by 50 GHz, the path module 91 separates the channels (λ1, λ3, λ5 ....) separated at 100 GHz. A first subband BB ′ having a frequency band and a second subband BB ″ band having channels (λ2, λ4, λ6 ....) separated at 100 GHz, and divided into a subband BB '. Similarly, the path modules 92 and 93 divide the RB1 band and the RB2 band into first subbands RB1 'and RB2' and second subbands RB1 "and RB2", respectively. .

Each path module 91-93 includes a coupler (not shown) having a first series of Bragg gratings attached to the first port and a second series attached to the second port. The Bragg grating attached to the first port has a reflection wavelength corresponding to each other channel (even channel), and the Bragg grating attached to the second port has a reflection wavelength corresponding to the remaining channel (odd channel). This grid arrangement doubles the channel-to-channel spacing to divide a single input path into two output paths.

After passing through the RPA unit 14, the BB, RB1, RB2 bands or respective subbands are received by the demultiplex unit 15. Referring to FIG. 8, the demultiplexer 15 receives six sub-multiplexers for receiving respective subbands BB ', BB ", RB1', RB1", RB2 ', and RB2 "and generating an output channel 17. As shown in FIG. (WD) (95 ', 95 ", 96', 96", 97 ', 97 "). The demultiplex unit 15 also includes receivers Rx1-Rx128 that receive the output channel 17.

The wavelength demultiplexer consists of arrayed waveguide grating elements, but modifications are also envisioned to achieve the same or similar wavelength separation. For example, an interference filter, Fabry-Perot filter, or intrafibre bragg in a conventional manner that demultiplexes channels in subbands (BB ', BB ", RB1', RB1", RB2 ', RB2 "). Lattice can be used.

The demultiplexer configuration 15 combines the interference filter and the AWG filter technology. Alternatively, a Fabry-Perot filter or intrafibrous Bragg grating may be used. WD (95 ', 95 "), which is an eight-channel demultiplexer with interference filter, receives and demultiplexes the first subband (BB') and the second subband (BB"), respectively. Specifically, the WD 95 'demultiplexes the channels [lambda] 1, [lambda] 3 ... [lambda] 15 and WD 95 "to the channels [lambda] 2, [lambda] 4 .... [lambda] 16. However, both WDs 95' ) And WD 95 "are 1x8 type AWG 100 GHz demultiplexers. Similarly, WD 96 'and WD 96" designate a first subband RB' and a second subband RB ", respectively. Receive and demultiplex to generate channels λ17-λ64, and WD 97 'and WD 97 " receive the first subband RB1' and the second subband RB1 ", respectively. Multiplex to generate channels λ 65 -λ 128. Both WD 96 'and WD 96 " are underequipped 1x32 type AWG 100 GHz demultiplexers using only 24 demultiplexer ports and WD (97'). ) And WD (97 ") are 1x32 type AWG 100 GHz demultiplexers using all possible demultiplexer ports. Output channels 17 are WD (95 ', 95", 96', 96 ", 97 ', 97"). Each output channel 17 is demultiplexed by a separate channel, and each output channel 17 is connected to one of the receivers Rx1-Rx128. It is received.

9 is for the optical amplifier 100 of the present invention. The optical amplifier 100 is usable in the optical transmission system 1, both in the amplifier section 53 of FIG. 4 and in the amplifier section 69 of FIG. 6 to amplify the signals in the RB2 band.

Amplifier 100 is a bi-directionally pumped optical amplifier, the input port 101 for the input of the optical signal to be amplified, the output port 102 for the output of the optical signal after amplification, and the optical input port 101 An active fiber 103 suitable for amplifying an optical signal having a combined first end 103a and a second end 103b optically coupled to the output port 102, and in a co-transfer direction with respect to the transmitted signal. A first pump source 104 suitable for supplying the first pump radiation to the active fiber 103 and optically coupled to the active fiber 103 by means of an optocoupler 105 and in the direction of simultaneous transmission with respect to the transmitted signal. A second pump source 106 is optically coupled to the active fiber 103 by a second optocoupler 107 and adapted to supply a second pump radiation to the active fiber 103.

Alternatively, by appropriately multiplexing the first pump radiation, the second pump radiation, and the optical signal, the first and second pump radiations in the same direction, preferably in both co-transfer directions, the active fibers 103 Supplied to.

A plurality of pump sources may be used instead of the first pump source and / or the second pump source. Multiple pump sources are multiplexed with wavelength or polarity (if operating at other wavelengths).

The amplifier 100 may be configured from the first optical insulator 108 and / or the second coupler 107 located between the input 101 and the first coupler 105 to optically transmit only from the input 101 to the coupler 105. It consists of a second insulator 109 located between the second coupler 107 and the output 102 to only optically transmit up to the output 102.

The active fiber 103 is a silica fiber co-doped with erbium and ytterbium. The active fiber 103 is monomode and has a length configured between 10 m and 30 m and a numerical aperture NA configured between 0.15-0.22. The shim of the active fiber 103 comprises components of the indicated concentration, i.e. 0.1-13 atomic% aluminum, 0.1-30 atomic% phosphorus, 0.1-0.6 atomic% erbium, 0.5-3.5 atomic% ytterbium.

The ratio between erbium and ytterbium concentrations ranges from 1: 5 to 1:30, for example 1:20.

The first coupler 105 has a first access fiber 105a optically coupled to the input port 101 to receive a signal (of an RB2 band channel) to be amplified, and a first pump source (e.g., a single mode optical fiber 110). The second access fiber 105b optically coupled to 104 to receive the first pump radiation, and the active fiber to supply the active fiber 103 with an optical signal to be amplified (in the same delivery direction) as the first pump radiation. A micro optical interference WDM coupler comprising a third access fiber 105c optically coupled to 103.

The first coupler also includes a converging lens system (not shown) and a selective reflection surface (not shown) such as a dichroic mirror to properly direct the light beam into the access fiber. The actual slope of the reflector surface inside the coupler depends on the direction of the incoming light beam carrying the signal and pump radiation. The select-reflective surface in coupler 105 is transparent to the wavelength of the RB2 band channel and reflects to the wavelength of the first pump radiation. In this way, the RB2 band channel passes through the reflective surface without loss when the first pump radiation is reflected by the reflective surface to the shim of the active fiber 103. Alternatively, the first coupler 105 includes a select-reflective surface that reflects the wavelength on the RB2 band channel and transmits the wavelength of the first pump radiation.

The first coupler 105 has an insertion loss for an optical signal of 0.6 dB or less. For example, the first coupler 105 is Oplink's model MWDM-45 / 54.

According to another embodiment of the invention, the first coupler 105 is a fiber fused like a coupler.

The second coupler 107 is provided by the optical fiber 111 to receive the pump radiation and the first access fiber 107a optically coupled to the output port 102 to supply the amplified signal to the output port 102. The second access fiber 107b optically coupled to the second pump source 106 and the optical signal amplified from the active fiber 103 are received and pump radiation generated by the second pump source 106 is converted into active fiber ( And a fused fiber WDM coupler including a third access fiber 107c optically coupled to the active fiber 103 and a fourth access fiber 107d having a free end and a low reflection terminal.

The second coupler 107 is a first fiber defining a first access fiber 107a and a third access fiber 107c and a second fiber defining a second access fiber 107b and a fourth access fiber 107d. By fuse.

The second coupler 107 has an insertion loss for an optical signal of 0.3 dB or less.

The first pump source 104 is a semiconductor laser diode that provides pump radiation at a wavelength in the range of 1465 nm-1495 nm, which is suitable for exciting erbium ions in the active fiber 103. The pump power provided by the first pump source 104 is comprised between 40 mW and 150 mW. The first pump source 104 is, for example, model number SLA5600-DA of Sumitomo Electric Industries, Ltd.

Direct pumping (especially co-directional pumping) of erbium ions is known to generate preamplification of the optical signal in the active fiber 103. This preamplification provides a boosting effect by pumping ytterbium ions, particularly at low input power conditions and is known to be a significant source of increased performance for the amplifier.

Applicants have found that it is desirable to directly pump erbium ions in the 1480 nm band for pumping in the 980 nm band. In fact, 1480 nm pump spinning differs from that occurring up to 980 nm pump spinning, which appears to be slowly absorbed from the active fiber to provide high fluorescence at long wavelengths (1600 nm). This causes the optical signal power to rise rapidly along the active fiber while avoiding excessive ASE integration.

The proposed amplifier can amplify the optical signal with very low input power up to -25dBm.

Referring to FIG. 10, the second pump source 106 includes a fiber laser 112 and a pump laser diode 113. The fiber laser 112 is suitable for generating a second pump radiation at a wavelength in the range between 1000 nm and 1100 nm and exciting ytterbium in the active fiber 103. The fiber laser 112 is composed of a double coated fiber 114, a first Bragg grating 118 and a second Bragg grating 119. Bragg gratings 118 and 119 are recorded at opposite ends of the double coated fiber 114 and delimit the Fabry-Perot resonance cavity of the fiber laser 112.

The pump laser diode 113 is a light area laser with emission spectra centered at a wavelength suitable for pumping dopant ions in the double coated fiber 114 comprised between 910 nm and 925 nm. The pump laser diode 113 has the same diameter seam with the same numerical aperture of the inner coating 116 of the active fiber 114 in order to couple the female radiation into the active fiber 114 with very high efficiency (close to 100%). The output is provided to the multimode optical fiber 120.

11B, under normal conditions, the pump spinning generated by the pump laser diode 113 is supplied to the inner coating 116 while exciting the ytterbium ions and is progressively absorbed by the shim 115. The de-excitement of ytterbium ions gives a radio stimulus in the wavelength range of 1000-1100 nm, transfers it to the seam 115, and amplifies itself. The gratings 118 and 119 reflect certain wavelengths in the range of 1000-1100 nm (e.g. 1047 nm) and emit a specific wavelength radiated from the end of the fiber 114 opposite the pump laser diode 113 after several reflections. Causes high power laser radiation.

The fiber laser 112 first generates the coated fiber 114 with the most utilized characteristics (length, geometry, components) according to the desired laser operation, and then attaches to the gratings 118 and 119 on opposite ends of the fiber 114. Is realized.

Two different preforms (not shown) are used to produce the fibers 114. The first preform is used to obtain the interior of the shim 115 and the inner covering 116. This preformation is achieved by treating SiO 2, P 2 O 5, Al 2 O 3 by chemical vapor deposition (CVD) and introducing rare earth oxide yttrium by the “solubility” method. The first preform serves properly to reduce the external diameter to a predetermined value.

The commercial preform of the second preform is used to obtain the exterior of the inner coating 116 and the outer coating 117. The second preform has a central region of pure SiO 2 and a peripheral region of the fluoride doped SiO 2. The central region of the second preform is partially removed to obtain a central longitudinal hole having a diameter slightly larger than the outer diameter of the first preform and the first preform is introduced therein. Internal coating is defined in part from the second preliminary run and in part from the first preform.

The three layer preformation thus obtained is obtained in the usual way to obtain the optical fiber 114.

The gratings 118 and 119 are recorded according to the technique developed and described by the applicants below and by the grating recording assembly 130 (FIG. 12).

12, the grating recording assembly 130, the pump laser diode 113 optically coupled to the first end 114a of the fiber 114, the optical power measurement element 131, and the second end of the fiber 114. There is a power meter located in front of 114b, a broadband pass filter 132 fitted to the second end 114b of the fiber 114 and the measurement element 131.

The measuring element 131 is, for example, a power meter of type ANDOAQ2140.

Filter 132 is an interference filter centered at a predetermined wavelength with respect to laser radiation (λ _laser) of the original 106. The

The assembly 130 is characterized by a specific software (Labview) by a processor (PC) 134 and a digital-to-analog converter (DAC) 133 suitable for controlling the pump laser diode 113. Device 131 using the < RTI ID = 0.0 > The DAC 133 is, for example, National Instruments PCI6110E. 12, the processor 134 is suitable for providing the P _out / P _pump characteristics of the laser 106 during the grating recording process in accordance with the information provided by the measuring element 131. As shown in FIG.

In addition, the assembly 130 includes a UV recording element 135 suitable for recording the gratings 118, 119 on the fibers 114. The UV recording device 135 includes an excimer ray storage value.

A method of recording the first grating 118 will be described with reference to the flux diagram in FIG. 16 and the configuration diagram in FIG. 18A. The method further comprises that the reflecting surface has a broader reflecting wavelength band than the reflecting wavelength expected for the first grating, so that at least about 4% of the interface of the fiber 114 is reached to reach a predetermined reflectance (R2) in the interface glass / air. 2 end 114b is cut and cleaned (block 200) to define the reflective surface bonded to the active fibers,

Pump radiation having optical power (P _in ) is supplied to the active fiber 114 by the pump laser diode 113 to excite the dopant ions and increase the amplified induced emission (ASE), which defines free emission.

The first grating 118 changes in reflectance R1 and the induced emission moves forward and backward in the fiber 114 as the second end 114b of the fiber 114 and as laser radiation at the wavelength λ _laser . The first grating 118 proximate the first end 114a of the fiber 114 by the UV recording device 105 in a space period corresponding to a predetermined laser wavelength (λ _laser ) in defining the resonant cavity that enables output. ),

The minimum value of pump radiation power with laser emission defines the threshold power (P _th ) according to the lattice intensity and is pumped by the processor 134 and the DAC 133 when the scan period is for example 15-20. By repeating scanning of the power of the pump spinning in the predetermined power range (starting at zero power) during the recording step (block 230),

Spectroscopically filter (block 240) the light radiation output from the second end 114b of the filter 114 by the filter 132 in filtering filtering the remaining pump radiation and free running radiation early in the recording process,

Measuring optical power includes obtaining a predetermined number N of optical power values during a scanning period, each value being obtained by calculating an average value of power detected in a predetermined measurement period (e.g., 2). The predetermined number N of power values and the predetermined measurement period are related to the value of the scanning period, so that the optical power of the output radiation filtered during the recording and scanning steps is measured by the measuring element 131 (block 250). ,

Performing linear regression consists of finding the best-fitting line of the N last point _{in the} P _out / P _in characteristic and evaluating the slope and intersection of the straight line with the P _in axis to obtain the current value (η, P _th ). In order to obtain the efficiency (η) and critical power (P _th ) of the laser, the optical power measured by the new return is processed (block 260),

The present value η _curr of the efficiency η is related to the present value of the first grating reflectance R ₁ , so that if the efficiency η increases, the present value of η (A point in FIG. 18A, η _curr ), The value of η in relation to the last scan cycle is checked against the previous value of η (B point in FIG. 18A, η _prec ), ie, obtained at the previous stage of the process and related to the previous scan cycle (block 270),

If the efficiency (η) increases (η _curr > η _prec ), repeat the process of recording, scanning, filtering, monitoring, processing and checking (blocks 220-270),

η _limit corresponds to the maximum value for the reflectance R ₁ of the first grating 108 and is the maximum efficiency that can be obtained with the consideration of R ₂ (4%), and detects if the recording process continues beyond this point. In relation to some inflow phenomena, such as the reduction of the central saturation and the interfering ray coordination, due to lattice deterioration, the efficiency (η) reaches a _limit (η _limit ) at a decrease (point D in FIG. 18A) ( C point in FIG. 18A), if no further increase (η _curr η _prec ) stops the process when the laser efficiency η decreases (block 280),

Evaluating the final reflectance of the first grating 118 according to the efficiency limit value η _limit (block 290).

The process of recording the first grid requires a total period of several minutes.

The first grating has a reflected wavelength band between 0.3 nm and 1 nm, preferably 0.4 nm and 0.7 nm.

The reflective surface used in the first step is also defined by a multi-layer interference reflective surface on the second end 114b, a fiber part comprising a grating, a semi-reflective mirror or a micro-optical component such as a lens system or the like.

The applicant has found that the threshold power P _th is another parameter that can be set when the first grating recording should be stopped in addition to the efficiency. In practice, the threshold power P _th decreases during the recording process and reaches the limit value P _th , limit when the efficiency reaches its limit η _limit . However, the Applicant has found that the evaluation of P _th is more difficult than the evaluation of η and that the change of P _th during the recording process is less than the change of η. In addition, the actual value of P _th is somewhat more difficult than the value that can be obtained from the preceding return. Therefore, we have found that η is the preferred parameter to be used in the check step.

The time efficiency η _limit obtained at the end of the process does not correspond to the maximum efficiency η _max that can be obtained for the fiber laser 112 (E point in FIG. 18A). In order to reach the maximum efficiency η _max , it is necessary to record the second grating 119 and make the most of its reflectance.

Recording only the first grating 118 is sufficient in some applications where the reflectivity of the second end of the active fiber 114 defines a laser cavity with the desired characteristics. For example, a 4% reflectance of the second end of the active fiber 114 is sufficient for an "in-air laser" where the output radiation is directed directly to the atmosphere.

Considering more careful use, it has been found that the second grating 119 with a reflectance of more than 4% improves the performance of the fiber laser 112.

Further attention should be paid to the actual grating assignment of the second grating 119, however, previous recording techniques are also suitable for recording the second grating 119. This is because the active fiber 114 changes its refractive index and the lattice wavelength peak varies during the recording step. In order to cure this disadvantage, the second grating 119 is a large band lattice, so that the peak shift is included in the band of the grating. The ratio between the reflection band of the second grating and the reflection band of the first grating is between 1.5 and 3. If a "phase mask" recording technique is used, a grating with an enlarged reflection band is obtained by placing a screen of slit in front of the mask and introduces some diffraction of UV refraction.

In order to overlap the peaks related to the first grating 118 and the peaks related to the second grating 118, a priori evaluation of possible peak variations during recording is made. This evaluation is made by estimating the required period of the recording process and the approximate variation per second of the grid peaks.

A method of recording the second grating 119 will be described with reference to the flux diagram of FIG. 17 and the configuration diagram of FIG. 18B. The method,

The second end 114b of the active fiber 114 is cut (block 300) to yield a 7-8 ° inclined surface (with respect to a plane perpendicular to the fiber axis) with a slight reflectivity to form an end, and the active fiber In order to excite the dopant ions of 114, pump radiation having optical power (Pin) is supplied to the active fiber 114 by the pump laser diode 113 (block 310),

The second grating 119 is a first grating 118 with varying reflectance R ₂ and a reflectance R ₁ close to 100%, causing the induced emission to advance back and forth in the fiber 114 and at wavelength λ _laser . In the definition of the resonant cavity output as laser radiation in the second grating (near the second end 114b of the fiber 114 by the UV recording element 105 at a space period corresponding to a predetermined laser wavelength (λ _laser ) 119) (block 320),

The minimum value of pump radiation power with laser radiation defines the threshold power (P _th ) according to the lattice intensity and is predetermined during the recording step by driving the pump laser diode 113 by the processor 134 and the DAC 133. Repeatedly scan the power of the pump spinning in the power range (different from the range used for the first grating recording) (block 330),

Spectral filtering (block 340) the light radiation output from the second end 114b of the filter 114 by the filter 132 in the filtering inhibiting free running radiation at the beginning of the residual pump radiation and the second grating recording. ,

Measuring optical power includes obtaining a predetermined number N 'of optical power values (different from a predetermined number N used for the first grating recording) during the scanning period, each value being a predetermined measurement period. Is obtained by calculating an average value of the power detected at. The predetermined number (N ′) of optical power values and the predetermined measurement period are related to the period of the scanning period, so that the optical power of the output radiation filtered during the recording and scanning steps Is measured by the measuring element 131 (block 350),

Performing linear regression finds the best-fit straight line of the last point of N '(corresponding to the N' optical power value obtained during the last scan cycle) and obtains the current values (η, P _th ) _{in the} P _out / P _in characteristic. Is calculated by evaluating the inclination and intersection of the straight line with the P _in axis, and the first detection value of η is the laser efficiency (η) in the middle of 0 and the limit value (η _limit ) found at the end of the first grating recording. Process the measured optical power by performing a new return to obtain and critical power (P _th ) (block 360),

The present value η _curr of the efficiency η is related to the present value of the second grating reflectance R ₂ , so that if the efficiency η increases, the present value of η (A point in FIG. 18B, η _curr ), The value of η in relation to the last scan cycle is checked against the previous value of η (B point in FIG. 18B, η _prec ), ie compared to that obtained at the previous stage of the process and related to the previous injection cycle (block 370)

If the efficiency (η) increases (ηcurr> ηprec), repeat the process of recording, scanning, filtering, monitoring, processing and checking (blocks 320-370),

The η _limit corresponds to the optimum value (R ₂ .pot) for the reflectance (R ₂ ) of the second grating 109 (for example comprised between 4-10%) and is to be obtained for the fiber laser 112. If the recording process continues beyond this point, η decreases due to lattice deterioration with respect to some inflow phenomena such as saturation of the detection center and reduction of interfering ray wrinkle contrast (D point in Fig. 18B). If the efficiency η reaches the _limit η _limit (point E in FIG. 18B) and no longer increases (η _curr η _prec ) Stop the process when the laser efficiency (η) decreases (block 380)

Evaluating the final reflectance of the second grating 119 according to the efficiency maximum value η _max (block 390).

During the second lattice writing process (R ₂ increase) the critical power P _th gradually decreases and this trend continues through the optimum value R ₂ .opt. Lowering the critical power P _th value is advantageous in that it allows lasers with low input power. Therefore, an improved standard that takes full advantage of fiber laser 112 implementation is to stop the process when a certain relationship or best compromise between efficiency η and critical power P _th is reached.

This compromise depends on the specific application under consideration.

Experimental Results for Implementability of Amplifier 100

Experimental measurements were performed on the amplifier 100.

The active fiber 103 used in the experiment has a diameter of 4.3 m, a coating diameter of 125 m, and a numerical aperture (NA) of 0.2.

element Si Al P Er Yb atom% 70.8 1.5 25 0.125 2.5

Erbium and ytterbium concentrations are about 1:20.

The first coupler 105 is the interference filter model MWDM-45 / 54 of Oplink. The first coupler 105 has an insertion loss of 0.6 dB.

The second coupler 107 is a fused fiber WDM coupler. The second coupler 107 is made by fusing the first fiber defining the access fibers 107a and 107c and the second fiber defining the access fibers 107b and 107d. The first fiber is an SM (single mode) fiber having a core diameter of 3.6 mu m, a coating diameter of 125 mu m, and a numerical aperture NA = 0.195. The second fiber is an SM filter having a core diameter of 3.6 mu m, a coating diameter of 125 mu m, and a numerical aperture NA = 0.195. Both SM filters are of Corning's CS 980 type. The second coupler 107 has an insertion loss of 1 dB.

A first pump source 104 suitable for providing pump radiation power of 50-70 mW at 1480 nm is a laser diode. The fiber 110 is an SM filter.

The second pump source 106 is Applicant's and is suitable to provide 500-650 mW of pump radiation power at 1047 nm. The fiber 111 is an SM fiber. The wide area diode laser 113 is suitable for providing 800 mW of radiation power at 915 nm. Applicant has found that the high saturation power of the amplifier is obtained using a much more powerful wide area diode laser.

The active fibers 114 in the first pump source are detected by SEM analysis and are shown in the table below.

element Si Ge Al P Yb atom% 89.40 2.78 1.17 5.93 0.72

In order to obtain high concentrations of ytterbium, the aluminum concentration was chosen high. The germanium concentration is low due to the high refractive index determined by the high concentrations of aluminum and ytterbium. Phosphorus was added to reduce the numerical aperture (NA) of the fibers.

The length of the active fiber 114 is 10 m and its curved diameter is 10 mm. Applicants have found that the bending diameter value represents the best compromise between the absorption efficiency and induced loss of the fiber.

The length of the resonant cavity (the distance between the first grating 118 and the second grating 119) is 10 m.

The active fiber 114 has an outer diameter of about 90 μm of the outer coating 117, an outer diameter of about 45 μm of the inner coating 116, and an outer diameter of about 4.5 μm of the shim 115. The refractive index step Δn = n1-n2 between the shim 115 and the inner coating 116 is 0.0083 and the refractive index step Δn '= n2-n3 between the inner coating 116 and the outer coating 117 is 0.067. Shim 115 and inner coating 116 define a single mode wavelength for the transmission of a transmission signal having a first numerical aperture NA1 of 0.155 and inner coating 116 and outer coating 117 are 0.22 second. Define a multimode wavelength for delivering pump radiation with a numerical aperture (NA2).

The gratings 118 and 119 are realized in the manner described above. The gratings 118 and 119 have a Bragg wavelength of 1047 nm. The first grating 118 has a reflectance of 99% at the peak wavelength and the second grating 118 has a reflectance of 10% or less at the same wavelength.

13 shows the response curve of the fiber laser 112. In particular, FIG. 13 shows the dependent state of the optical power Pout of the laser radiation emitted on the pump power Pin provided by the laser diode 113. According to the obtained curve, the laser source has an efficiency of η = 81.5% and a critical power of P _th = 99 mW.

14 shows the second end of the fiber 103 and the output 102 between the input 101 and the first end of the fiber 103 (ie, the first opto-insulator 108 and the first optocoupler 105). (I.e., insertion loss due to the passive components of the amplifier 100 respectively positioned between the second optocoupler 107 and the second opto-isolator 109). The characteristics of FIG. 14 are obtained by a spectrophotometer.

Fig. 15 shows the gain curve of the amplifier 100 for the wavelength scanning of the input signal from 1575 nm to 1620 nm. Other curves in FIG. 15 represent the input signal power in the range of 25 dBm-10 dBm. For input signal power greater than 0 dBm, the amplifier 100 provides an output power greater than 18 dBm and can be used as a booster amplifier. In particular, at 10 dBm input signal power, the amplifier provides up to 22 dBm output power with a maximum gain change of less than 1 dB in the RB2 band.

When the amplifier 100 is used as a booster with an input signal of 10 dBm or more, the gain curve shows a maximum change of 1 dB or more in the RB2 band.

In addition, the amplifier 100 shows gains extending beyond the RB2 band to 1620 nm.

Numerical Results of Grid Recording Method Simulation

19-21 show numerical results obtained by simulating a lattice recording method on an active fiber 114 having the properties listed in the above experimental measurements.

FIG. 19 shows the dependence of the light output power P _out on the pump light power P _in for different values of the first grating reflectivity during the first grating recording process. The resonant cavity is defined by the first grating 118 and the second end 114b (4% reflectivity) of the fiber 114. As with the first grating reflectance, a gradual increase in fiber laser efficiency and a gradual decrease in critical power P _th can be seen.

20 shows the dependence of the efficiency η of the fiber laser 112 and the critical power P _th on the first grating reflectivity during the first grating recording process. Each point for the η and P _th characteristics corresponds to a straight line in FIG. 19.

FIG. 21 shows the dependence of the efficiency η of the fiber laser 112 and the critical power P _th on the second grating reflectance during the second grating recording process, assuming that the first grating reflectance is 99%. The maximum in the efficiency curve is separable with a value of at least 80% for a second grating reflectance of 4%. If the best compromise (between η and P _th ) standards are used, the recording process should be stopped when the second grating reflectance is 4-10%.

Claims (26)

In the optical transmission system, An optical transmitter 10 for transmitting an optical signal, An optical receiver 20 for receiving the optical signal; An optical fiber link 30 suitable for optically coupling the transmitter to the receiver and for transmitting the optical signal; Comprising an optical amplifier 100 coupled along the link to be suitable for amplifying the optical signal, the optical amplifier 100, An input 101 for inputting the optical signal, An output 102 for outputting the optical signal; Active fiber co-doped with erbium and ytterbium having a first end 103a optically coupled to the input 101 and a second end 103b optically coupled to the output 102 to amplify the optical signal ( 103), A first pump source 104 and a second pump source 106 generating first pump radiation and second pump radiation, respectively, It consists of a first optical coupler 105 and a second optical coupler 107 for optically coupling the first pump source 104 and the second pump source 106 to the active fiber 103, Wherein said first pump radiation comprises an excitation wavelength for erbium and said second pump radiation comprises an excitation wavelength for ytterbium. The method of claim 1, The optical amplifier 100 has a wavelength amplifier band of 1565 nm or more. The method of claim 1, The first optical coupler 105 is optically coupled to the first end 103a of the active fiber 103 to supply the first pump radiation to the active fiber 103 in the co-transfer direction with respect to the optical signal, and the second The optical coupler 106 is optically coupled to the second end 103b of the active fiber 103 in order to supply a second pump radiation to the active fiber 103 in the direction of reversal of the optical signal. system. The method of claim 1, The active fiber 103 is a light transmission system, characterized in that the single coated fiber. The method of claim 1, The active fiber 103 is a light transmission system, characterized in that the single-mode fiber. The method of claim 1, The first pump radiation has a wavelength between 1465 nm and 1495 nm. The method of claim 1, And the second pump radiation has a wavelength between 1000 nm and 1100 nm. The method of claim 1, Optical transmission system, characterized in that the first optical coupler (105) is a micro optical WDM coupler. The method of claim 1, Optical transmission system, characterized in that the second optical coupler (107) is a fused fiber WDM coupler. In the method for amplifying an optical signal, Supplying an optical signal to an active fiber co-doped with erbium and ytterbium, Optically pumping the active fiber during the step of supplying the optical signal, the optical pumping step comprising supplying the active fiber with a first pump radiation to excite erbium and a second pump radiation to excite ytterbium Characterized in that. The method of claim 10, The step of supplying the first pump radiation is supplying the first pump radiation to the active fiber in the co-transfer direction with respect to the optical signal, and the step of supplying the second pump radiation is the optical signal for the second pump radiation Method for supplying the active fiber in the direction of reversal with respect to. The method of claim 10, The step of supplying the first pump spinning to the active fiber, characterized in that it comprises supplying the active fiber excitation radiation for erbium having a wavelength between 1465 nm and 1495 nm. The method of claim 10, And supplying the second pump spinning to the active fiber comprises supplying excitation radiation for erbium having a wavelength between 1000 nm and 1100 nm to the active fiber. The method of claim 10, The active fiber includes a seam and a sheath, and the step of supplying the first pump spinning and the second pump spinning to the active fiber is characterized in that the supply of the first pump spinning and the second pump spinning to the core of the active fiber How to. The method of claim 10, Supplying an optical signal to the active fiber comprises supplying to an active fiber optical signal having a wavelength of at least 1565 nm. In the optical amplifier, An input 101 for inputting an optical signal, An output 102 for outputting the optical signal; Active fibers 103 co-doped with erbium and ytterbium that are optically coupled to the input and the output and are suitable for amplifying the optical signal; It consists of a first optical coupler 105 and a second optical coupler 107 for optically coupling the first pump source 104 and the second pump source 106 to the active fiber, respectively, the first pump spinning Is an excitation wavelength for erbium and the second pump radiation comprises an excitation wavelength for ytterbium. The method of claim 16, The excitation wavelength for erbium is between 1465 nm-1495 nm and the excitation wavelength for ytterbium is between 1000 nm-1100 nm. The method of claim 16, The first optical coupler 105 is connected between the input 101 and the active fiber 103 to supply a first pump radiation to the active fiber 103 in the co-transfer direction for the optical signal, the first The optical coupler 107 is connected between the output 102 and the active fiber 103 to supply a second pump radiation to the active fiber 103 in the anti-moon direction for the optical signal amplifier. The method of claim 16, The active fiber 103 is an optical amplifier, characterized in that the single-coated and single-mode fibers. The method of claim 16, The first optical coupler 105 is an optical amplifier, characterized in that the micro-optical WDM coupler. The method of claim 16, And wherein said second optocoupler is a fused-optical WDM coupler. The method of claim 16, The second pump source 106 includes other active fibers 114 and a fiber laser 112 suitable for generating the second pump spinning and a pump laser source 113 suitable for pumping the active fibers 114. Optical amplifier, characterized in that consisting of). The method of claim 22, The other active fiber 114 is an optical amplifier, characterized in that the double coated fiber. The method of claim 22, The other active fiber 114 is an optical amplifier, characterized in that it comprises an optical fiber doped with erbium. The method of claim 22, The fiber laser (112) is characterized in that it comprises a first Bragg grating (118) and a second Bragg grating (119) recorded on opposite ends of the other active fibers (114). The method of claim 22, The pump laser source 113 is an optical amplifier, characterized in that the optical area laser diode.