The gain medium of an optical amplifier can only achieve a limited gain. One approach achieves higher gain by geometrically setting up light so that it passes through multiple channels as it passes through the amplifier, known as a multipass amplifier. The simplest is a two-pass amplifier, where the beam passes through the crystal twice, usually with exactly or nearly opposite directions of propagation.
Time-domain OCT is mainly composed of Michelson interferometers. The light emitted by the light source is divided into two beams after passing through the coupler, and enters the sample arm and the reference arm of the Michelson interferometer respectively.
The eye diagram is a series of digital signals accumulated and displayed on the oscilloscope. It contains a wealth of information. From the eye diagram, the influence of intersymbol crosstalk and noise can be observed, which reflects the overall characteristics of the digital signal, so as to estimate the system optimization. Therefore, eye diagram analysis is the core of signal integrity analysis for high-speed interconnect systems.
Single-frequency lasers based on Er3+-doped or Er3+/Yb3+ co-doped gain fibers mainly work in the 1.5 μm band (C-band: 1530-1565 nm) and part of the L-band (1565-1625 nm). Its wavelength is in the C window of optical fiber communication, which makes the 1.5 μm band single-frequency fiber laser with narrow linewidth and low noise characteristics very important in coherent optical communication. It is used in high-resolution sensing, optical frequency domain reflectometer , laser radar and other fields also have a wide range of applications.
Some solid-state laser gain media are doped with transition metal ions, and the transitions involved are those of electrons in the three-dimensional shell. Figure 1 shows the commonly used transition metal ions and their host media.
Optical fiber array, using a V-groove (V-Groove) substrate, a bundle of optical fibers or an optical fiber ribbon is installed on the substrate at specified intervals to form an array.