Chapter 6
Photodetection Devices
Abstract The two main photodetection devices used in optical fiber communications are semiconductor-based pin photodiodes and avalanche photodiodes. The key
advantages of these devices are their size compatibility with optical fibers, their high
sensitivities at the desired operational wavelengths, and their fast response times that
allow accurate signal tracking. Because optical signals generally are weakened and
distorted when they emerge from the end of a fiber, the photodiodes must meet specific
stringent performance requirements. The purpose of this chapter is to describe the
performance characteristics and show how the photodiodes are used in optical fiber
links.
At the output end of an optical transmission line, there must be a receiving device
that interprets the information contained in the optical signal. The first component
of this receiver is a photodetector. The photodetector senses the luminescent power
falling upon it and converts the variation of this optical power into a correspondingly varying electric current. The optical signal is generally weakened and distorted
when it emerges from the end of the fiber, the photodetector must meet very high
performance requirements. Among the foremost of these requirements are a high
response or sensitivity in the emission wavelength range of the optical source being
used, a minimum addition of noise to the system, and a fast response speed or sufficient bandwidth to handle the desired data rate. The photodetector should also be
insensitive to variations in temperature, be compatible with the physical dimensions
of the optical fiber, have a reasonable cost in relation to the other components of the
system, and have a long operating life.
Among the different photodetectors are photomultipliers, pyroelectric detectors,
and semiconductor-based photoconductors, phototransistors, and photodiodes. Of
these detectors, the semiconductor-based photodiode is used almost exclusively for
fiber optic systems because of its small size, suitable material, high sensitivity, and
fast response time. The two types of photodiodes used are the pin photodetector and
the avalanche photodiode (APD). The following sections examine the fundamental
characteristics of these two device types. The elementary principles of semiconductor
device physics given in Sect. 4.1 will be used in describing these components. Basic
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
G. Keiser, Fiber Optic Communications,
https://doi.org/10.1007/978-981-33-4665-9_6
241
Photodetection Devices
Abstract The two main photodetection devices used in optical fiber communications are semiconductor-based pin photodiodes and avalanche photodiodes. The key
advantages of these devices are their size compatibility with optical fibers, their high
sensitivities at the desired operational wavelengths, and their fast response times that
allow accurate signal tracking. Because optical signals generally are weakened and
distorted when they emerge from the end of a fiber, the photodiodes must meet specific
stringent performance requirements. The purpose of this chapter is to describe the
performance characteristics and show how the photodiodes are used in optical fiber
links.
At the output end of an optical transmission line, there must be a receiving device
that interprets the information contained in the optical signal. The first component
of this receiver is a photodetector. The photodetector senses the luminescent power
falling upon it and converts the variation of this optical power into a correspondingly varying electric current. The optical signal is generally weakened and distorted
when it emerges from the end of the fiber, the photodetector must meet very high
performance requirements. Among the foremost of these requirements are a high
response or sensitivity in the emission wavelength range of the optical source being
used, a minimum addition of noise to the system, and a fast response speed or sufficient bandwidth to handle the desired data rate. The photodetector should also be
insensitive to variations in temperature, be compatible with the physical dimensions
of the optical fiber, have a reasonable cost in relation to the other components of the
system, and have a long operating life.
Among the different photodetectors are photomultipliers, pyroelectric detectors,
and semiconductor-based photoconductors, phototransistors, and photodiodes. Of
these detectors, the semiconductor-based photodiode is used almost exclusively for
fiber optic systems because of its small size, suitable material, high sensitivity, and
fast response time. The two types of photodiodes used are the pin photodetector and
the avalanche photodiode (APD). The following sections examine the fundamental
characteristics of these two device types. The elementary principles of semiconductor
device physics given in Sect. 4.1 will be used in describing these components. Basic
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
G. Keiser, Fiber Optic Communications,
https://doi.org/10.1007/978-981-33-4665-9_6
241