Single-frequency fiber lasers have a very narrow limit linewidth, and their spectral line shape is Lorentz type, which is significantly different from single-frequency semiconductors. The reason is that single-frequency fiber lasers have longer laser resonant cavities and longer photon lifetimes in the cavity. This means that single-frequency fiber lasers have lower phase noise and frequency noise than single-frequency semiconductor lasers.
Generally speaking, when people talk about infrared light sources, they are referring to light with vacuum wavelengths greater than ~700–800 nm (the upper limit of the visible wavelength range).
laser distance measurng uses a laser as a light source for ranging. According to the way the laser works, it is divided into continuous optical devices and pulse lasers. Ammonia, gas ions, atmosphere temperature and other gas detectors work in a continuous forward state, used for phase laser ranging, dual heterogeneous semiconductor lasers, used for infrared ranging, ruby, gold glass and solid-state lasers , used for pulsed laser ranging.
Optical fiber amplifier refers to a new type of all-optical amplifier used in optical fiber communication lines to achieve signal amplification. Among the currently practical fiber amplifiers, there are mainly erbium-doped fiber amplifiers (EDFA), semiconductor optical amplifiers (SOA) and fiber Raman amplifiers (FRA). Among them, erbium-doped fiber amplifiers are now widely used in long-distance applications due to their superior performance. It is used as power amplifier, relay amplifier and preamplifier in the fields of long-distance, large-capacity and high-speed optical fiber communication systems, access networks, optical fiber CATV networks, systems (radar multi-channel data multiplexing, data transmission, guidance, etc.).
An optical fiber sensor is a sensor that converts the state of the measured object into a measurable light signal. The working principle of the optical fiber sensor is to send the incident light beam from the light source into the modulator through the optical fiber. The interaction between the modulator and the external measured parameters determines the optical properties of the light, such as the intensity, wavelength, frequency, phase, polarization state, etc. It changes and becomes a modulated optical signal, which is then sent to the optoelectronic device through the optical fiber and passed through the demodulator to obtain the measured parameters. During the whole process, the light beam is introduced through the optical fiber, passes through the modulator, and then emitted. The role of the optical fiber is first to transmit the light beam, and secondly to act as an optical modulator.
Fiber amplifier in a fiber optic data link, the amplification process that occurs over a very long transmission fiber.
