EDFA products are mainly concentrated in C-band 1530nm~1565nm and L-band 1565nm~1606nm, Currently EDFA C-band dominate the market, but more and more manufacturers will have to focus attention on the L-band. Future development requires more transmission bandwidths of 1250nm~1650nm for optical amplifiers, and Raman amplifiers within this bandwidth range are receiving more attention from the market. Usually there are mainly distributed Raman amplifiers and discrete Raman amplifiers.
Unlike EDFA, which uses erbium-doped fiber as the gain medium, the distributed Raman amplifier uses the transmission fiber in the system as its gain medium. Fiber Raman Amplifier FRA is stimulated Raman scattering of strong pump beams propagating through fiber. If a weak signal light and a strong pump light are simultaneously transmitted in an optical fiber and the wavelength of the weak signal light is within the Raman gain bandwidth of the pump light, the energy of the strong pump light is transferred to In the weak signal light, the weak signal light is amplified to obtain a Raman gain of about 10dB. The discrete Raman amplifier is close to EDFA, and uses a special fiber with a smaller core to amplify the signal inside the amplifier. The discrete Raman amplifier has a gain of about 30dB. With the rapid development of the current communications industry, the amount of information that needs to be exchanged increases exponentially, which requires the communications system to have higher transmission capacity. In short, the communication line needs a larger bandwidth. There are two measures to achieve bandwidth amplifiers. One is to achieve the purpose of bandwidth amplifiers through the use of multiple pumps. The more pumps, the greater the bandwidth. However, the increase in the number of pumps brings difficulties to its practical application, which not only increases the cost of the system, but also makes pump multiplexing more complicated, and makes it more difficult to balance the gain. Another measure is to use the industry's mature erbium-doped fiber amplifier EDFA technology to combine FRA and EDFA to construct a broadband amplifier, which can greatly reduce the number of pumps required while having a larger bandwidth, and gain equalization easy. Now it is not limited to simply combining FRA and EDFA. Instead, it uses the characteristics of distributed Raman amplification to use transmission fibers to combine FRA and EDFA in one module to mix Raman EDFA broadband amplifiers. Utilizing the low noise figure of the Raman amplifier not only improves the system's signal-to-noise ratio SONR, increases the transmission distance of the DWDM transmission system, but also reduces the transmission power at the input.
Communication technology changes with each passing day, and people have higher and higher requirements for information exchange speed, which requires ultra-high-speed, large-capacity communication equipment to meet these needs. The birth and development of EDFA meets these needs to a certain extent, but with the increase in communication transmission rate and the commercial use of DWDM from 32 wave, 40 wave band to 160 wave, this requires optical amplification equipment to have better Performance, the application of FRA+EDFA combination satisfies the current demand well. Future small modular, low cost, large bandwidth optical fiber amplifying device main direction of the product is iterative.