Optical fiber technology generally consists of three parts: optical signal transmitting end: optical fiber used to transmit optical signals; and optical signal receiving end.
The function of an optical signal transmitter is to convert the electrical signal to be transmitted into an optical signal via an electro-optical conversion device. Currently, the electro-optical conversion device at the transmitter generally uses a light-emitting diode (LED) or a semiconductor laser diode. LEDs have relatively low output optical power and a relatively low signal modulation rate, but they are inexpensive. Their output optical power and driving current are basically linearly related within a certain range, making them suitable for short-distance, low-speed, analog signal transmission. Laser diodes have high output power and a high signal modulation rate, but they are more expensive, making them suitable for long-distance, high-speed, digital signal transmission.
The function of optical fiber is to transmit optical signals from the transmitting end to the receiving end with the least possible attenuation and distortion. Currently, optical fibers generally use multimode or single-mode silica optical fibers with good transmittance in the near-infrared band of 0.84µm, 1.31µm, and 1.55µm.
The function of an optical signal receiver is to convert the optical signal back into a corresponding electrical signal via a photoelectric conversion device, which typically uses a semiconductor photodiode or an avalanche photodiode. The emission wavelength of the light source constituting the optical fiber transmission system must match the band in which the transmission fiber presents a low-loss window and the peak response band of the photoelectric detection device.
The transmitting electro-optical conversion device uses a high-brightness near-infrared semiconductor light-emitting diode with a center emission wavelength of 0.84µm, and the transmission optical fiber uses multimode silica fiber. The receiving photoelectric conversion device uses a silicon photodiode with a peak response wavelength of 0.8µm to 0.9µm. Further details on each component are provided below.
