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7 Optical Receiver Operation
criterion normally is specified in terms of a peak signal-to-rms-noise ratio. The calculation of the error probability for a digital optical communication receiver differs from
that of conventional electric systems. This is due to the discrete quantum nature of
the photon arrival and detection processes and the random gain fluctuations when an
avalanche photodiode is used. Researchers have used a variety of analytical methods
to derive approximate predictions for receiver performance. In carrying out these
analyses, one needs to make a tradeoff between calculation simplicity and accuracy of the approximation. General reviews and detailed concepts of optical receiver
designs are given in the literature [1–12].
First Sect. 7.1 presents an overview of the fundamental operational characteristics
of the various stages of an optical receiver. This consists of tracing the path of a digital
signal through the receiver and showing what happens at each step along the way.
Section 7.2 then outlines the fundamental methods for determining the bit-error rate
or probability of error (the chance that a bit is corrupted and received in error) of a
digital receiver based on signal-to-noise considerations. This section also discusses
the concept of receiver sensitivity, which is an important parameter for estimating
the minimum received optical power that is needed to achieve a specific probability
of error.
The eye diagram is a common measurement tool to determine the fidelity of the
received signal. Eye diagrams have been used extensively for all types of communication links, including wire lines, wireless systems, and optical links. Section 7.3
describes the method for generating an eye diagram and how to interpret various
signal fidelity parameters with it.
For passive optical network (PON) applications, the operational characteristics of
an optical receiver located at the central telecommunications switching office differ
significantly from receivers used in conventional point-to-point links. Section 7.4
gives a brief description of these devices, which are known as burst-mode receivers.
Finally, Sect. 7.5 describes another optical receiver type that is used for analog links.
7.1 Basic Receiver Operation
The design of an optical receiver can be quite sophisticated because the receiver
must be able to detect and interpret what type of data was sent based on an amplified and reshaped version of the weakened and distorted received signal. To get an
appreciation of the function of an optical receiver, first consider what happens to
a signal as it is sent through an optical fiber link. Because traditionally fiber optic
communication links are intensity-modulated direct-detection (IM-DD) systems that
use a binary on-off keyed (OOK) digital signal, Sect. 7.1.1 analyzes direct-detection
receiver performance by using this OOK signal format.
7 Optical Receiver Operation
criterion normally is specified in terms of a peak signal-to-rms-noise ratio. The calculation of the error probability for a digital optical communication receiver differs from
that of conventional electric systems. This is due to the discrete quantum nature of
the photon arrival and detection processes and the random gain fluctuations when an
avalanche photodiode is used. Researchers have used a variety of analytical methods
to derive approximate predictions for receiver performance. In carrying out these
analyses, one needs to make a tradeoff between calculation simplicity and accuracy of the approximation. General reviews and detailed concepts of optical receiver
designs are given in the literature [1–12].
First Sect. 7.1 presents an overview of the fundamental operational characteristics
of the various stages of an optical receiver. This consists of tracing the path of a digital
signal through the receiver and showing what happens at each step along the way.
Section 7.2 then outlines the fundamental methods for determining the bit-error rate
or probability of error (the chance that a bit is corrupted and received in error) of a
digital receiver based on signal-to-noise considerations. This section also discusses
the concept of receiver sensitivity, which is an important parameter for estimating
the minimum received optical power that is needed to achieve a specific probability
of error.
The eye diagram is a common measurement tool to determine the fidelity of the
received signal. Eye diagrams have been used extensively for all types of communication links, including wire lines, wireless systems, and optical links. Section 7.3
describes the method for generating an eye diagram and how to interpret various
signal fidelity parameters with it.
For passive optical network (PON) applications, the operational characteristics of
an optical receiver located at the central telecommunications switching office differ
significantly from receivers used in conventional point-to-point links. Section 7.4
gives a brief description of these devices, which are known as burst-mode receivers.
Finally, Sect. 7.5 describes another optical receiver type that is used for analog links.
7.1 Basic Receiver Operation
The design of an optical receiver can be quite sophisticated because the receiver
must be able to detect and interpret what type of data was sent based on an amplified and reshaped version of the weakened and distorted received signal. To get an
appreciation of the function of an optical receiver, first consider what happens to
a signal as it is sent through an optical fiber link. Because traditionally fiber optic
communication links are intensity-modulated direct-detection (IM-DD) systems that
use a binary on-off keyed (OOK) digital signal, Sect. 7.1.1 analyzes direct-detection
receiver performance by using this OOK signal format.