980nm pump laser application
The birth and development of optical fiber communication is an important revolution in the history of telecommunications. In recent years, with the technological progress, the reform of telecom management and the gradual opening of the telecommunications market, the development of optical fiber communication once again showing a new situation of vigorous development. At the same time due to the Internet. Interactive multimedia and other data services and the rapid development of mobile communication terminals increasingly popular, the signal transmission rate and transmission broadband requirements are getting higher and higher, especially for long-distance fiber optic backbone network and metro optical network communication capacity needs Increasingly, the improvement of system broadband is imperative. (WDM), especially dense wavelength division multiplexing (DWDM) is currently recognized as "the best solution for rapid growth of communication network bandwidth". In the future, whether it is wide area network, metropolitan area network or Network, DWDM for the transmission platform, DWDM-based optical transport network will constitute the basic physical layer of the entire communication network.
At present, the development trend of communication optical network is advancing to the client side, not only the backbone network popularized optical communication, metropolitan area network is also more and more use of optical communication, and access network also began to use optical communication, fiber to the home FTTH) is only a matter of time. For signal transmission, the signal relay amplification is essential, the most widely used EDFA, it is DWDM system and the future high-speed system, all-optical network indispensable one of the important devices.
EDFA pump source generally use 980nm and 1480nm high-power LD. The following work on the EDFA do a brief introduction. When the signal light is coupled with the pump light at the appropriate power, the erbium-doped fiber is passed through the isolator, and the signal light is amplified by the erbium-doped fiber under the action of the pump light. The erbium-doped fiber is an optical fiber with a certain concentration of Er 3+. In order to clarify its amplification principle i, it is necessary to start from the energy level diagram of erbium ions. The outer electrons of erbium ions have a three-level structure (E1, E2 and E3 in Figure 1-1), where E1 is the ground level, E2 is the metastable energy level, E3 is the high energy level, EDFA level map.
When the high-energy pump laser is used to excite the erbium-doped fiber, the bound electrons of erbium ions can be excited from the ground state energy level to the high energy level E3. However, the high energy level is unstable, so the erbium ions will soon undergo no radiation attenuation (ie, do not release photons) into the metastable energy level E2. And the E2 level is a metastable band at which the lifetime of the particles is long and the particles received by the pump laser are continuously collected in the form of nonradiative transitions, To achieve the number of particles inversion distribution. When an optical signal having a wavelength of 1550 nm passes through this erbium-doped fiber, the metastable particles transition to the ground state in the form of stimulated radiation and produce photons of the same photon as the incident light, thereby greatly increasing the signal light The number of photons, that is, to achieve the signal light in the erbium-doped fiber transmission process has been amplified function. As shown in Figure 1-2, the erbium-doped fiber amplifier works schematic.
EDFA according to the different pump source, can be divided into 980nm and 1480nm two. 1480nm pump gain is high, the maximum output power saturation; 980nm pump gain coefficient of the highest, the lowest noise. In the actual line amplifier applications, single-pump amplifiers are usually 980nm pump source; multi-stage amplifier is often used more than two pumps, the first level with 980nm pump source, the second level above 1480nm or 980nm pump source.
Not only in the communications industry 980nm high power pump laser has a wide range of applications in laser medical and other aspects of a larger application, medical proof, the surrounding tissue damage is small, and also has a good effect of coagulation hemostasis. So high-power 980nm semiconductor lasers are used for medical laser scalpels.
In the field of communication, the optical fiber is the main transmission channel, 980nm pump laser needs to be coupled with the fiber to use, how to laser light emitted by the chip as much as possible to effectively coupled to the fiber to become a hot spot, but also the laser package One of the key processes.