Chapter 7
Optical Receiver Operation
Abstract The design of an optical receiver can be quite sophisticated because the
receiver must be able to detect weak, distorted signals and make decisions on what
type of data was sent based on an amplified and reshaped version of this distorted
signal. In the photodetection processes, various noises and distortions will unavoidably be introduced, which can cause signal interpretation errors. Noise considerations
are thus important in the design of optical receivers, because the noise sources operating in the receiver generally set the lowest limit for the signal levels that can be
processed. This chapter describes the origins of these noises and their effect on link
performance.
Having discussed the characteristics and operation of photodetectors in the previous
chapter, the next step is to consider features of the optical receiver. An optical receiver
consists of a photodetector, an amplifier, and signal-processing circuitry. The receiver
has the task of first converting the optical energy emerging from the end of a fiber
into an electric signal, and then amplifying this signal to a large enough level so that
it can be processed by the electronics following the receiver amplifier.
In these processes, various noises and distortions will unavoidably be introduced,
which can lead to errors in the interpretation of the received signal. Depending on the
magnitude of the received optical signal, the current generated by the photodetector
could be very weak and is adversely affected by the random noises associated with
the photodetection process. When this electric signal output from the photodiode is
amplified, additional noises arising from the amplifier electronics will further corrupt
the signal. Noise considerations are thus important in the design of optical receivers,
because the noise sources operating in the receiver generally set the lowest limit for
the signals that can be processed.
In designing a receiver, it is desirable to predict its performance based on mathematical models of the various receiver stages. These models must take into account
the noises and distortions added to the signal by the components in each stage,
and they must show the designer which components to choose so that the desired
performance criteria of the receiver are met.
The average error probability is an especially meaningful criterion for measuring
the performance of a digital communication system. In an analog system the fidelity
© 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_7
267
Optical Receiver Operation
Abstract The design of an optical receiver can be quite sophisticated because the
receiver must be able to detect weak, distorted signals and make decisions on what
type of data was sent based on an amplified and reshaped version of this distorted
signal. In the photodetection processes, various noises and distortions will unavoidably be introduced, which can cause signal interpretation errors. Noise considerations
are thus important in the design of optical receivers, because the noise sources operating in the receiver generally set the lowest limit for the signal levels that can be
processed. This chapter describes the origins of these noises and their effect on link
performance.
Having discussed the characteristics and operation of photodetectors in the previous
chapter, the next step is to consider features of the optical receiver. An optical receiver
consists of a photodetector, an amplifier, and signal-processing circuitry. The receiver
has the task of first converting the optical energy emerging from the end of a fiber
into an electric signal, and then amplifying this signal to a large enough level so that
it can be processed by the electronics following the receiver amplifier.
In these processes, various noises and distortions will unavoidably be introduced,
which can lead to errors in the interpretation of the received signal. Depending on the
magnitude of the received optical signal, the current generated by the photodetector
could be very weak and is adversely affected by the random noises associated with
the photodetection process. When this electric signal output from the photodiode is
amplified, additional noises arising from the amplifier electronics will further corrupt
the signal. Noise considerations are thus important in the design of optical receivers,
because the noise sources operating in the receiver generally set the lowest limit for
the signals that can be processed.
In designing a receiver, it is desirable to predict its performance based on mathematical models of the various receiver stages. These models must take into account
the noises and distortions added to the signal by the components in each stage,
and they must show the designer which components to choose so that the desired
performance criteria of the receiver are met.
The average error probability is an especially meaningful criterion for measuring
the performance of a digital communication system. In an analog system the fidelity
© 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_7
267