Fiber optic sensors rely on thin, long optical fibers. For light waves to propagate normally within these fibers and meet measurement requirements, certain requirements are placed on the light source, including its structure and performance. This article will introduce some of the requirements for light sources in fiber optic sensors.
Firstly, due to the structural limitations of fiber optic sensors, the light source must be small to facilitate coupling with the fiber optic cable. The light source must also have sufficient brightness to increase the sensor's output optical power. The wavelength of the emitted light should be suitable to minimize energy loss during transmission through the fiber optic cable. Secondly, the light source needs to be stable, have low noise, and be able to operate continuously at room temperature for extended periods. It should also be easy to maintain and use.
Fiber optic sensors utilize a wide variety of light sources, which can be broadly categorized into coherent and incoherent sources based on their light coherence. Incoherent sources include incandescent light sources and light-emitting diodes (LEDs), while coherent sources include various lasers, such as helium-neon gas lasers and solid-state lasers. Coherent light sources are preferred in most fiber optic sensors.
The photodetector is also an important component of a fiber optic sensor. Its performance directly affects the sensor's performance; therefore, understanding it is crucial. The photodetectors used in fiber optic sensors are generally photoelectric sensors, whose function is to convert light energy into electrical energy.
Therefore, they are also called optoelectronic devices. Generally, fiber optic sensors require the following from their photodetectors: good linearity, proportionally converting optical signals into electrical signals; high sensitivity, able to detect minute input optical signals and output large electrical signals; wide response bandwidth, fast response speed, and good dynamic characteristics; stable performance and low noise.
