Chapter 8
Digital Optical Fiber Links
Abstract The design of a digital optical link involves many interrelated operating
characteristics of the fiber, source, photodetector, and other components in the link.
In carrying out an optical fiber link analysis, several iterations with different device
characteristics may be required before the analysis is completed satisfactorily. The
two basic analyses that usually are carried out to ensure that the desired system
performance can be met are the link power budget and the system rise-time analysis.
In addition to discussing these two analyses, this chapter addresses procedures for
detecting and controlling errors in a digital data stream in order to improve the
reliability of a communication link.
The preceding chapters have presented the fundamental characteristics of the individual building blocks of an optical fiber transmission link. These include the optical
fiber transmission medium, the optical source, and the photodetector and its associated receiver. Now this chapter will examine how these individual parts can be
put together to form a complete optical fiber transmission link. In particular, basic
digital links are addressed in this chapter, and analog links in Chap. 9. More complex
transmission links and networks are examined in Chap. 13.
The first discussion involves the simplest case of a point-to-point link. This
includes considering the transmitted signal format plus examining the components
that are available for a particular application and seeing how these components relate
to the system performance criteria. From a system performance viewpoint, the key
operating criteria include data timing extraction, signal dispersion, power penalties,
and bit error rate. For a given set of components and a given set of system requirements, a power budget analysis then is carried out to determine whether the fiber
optic link meets the attenuation requirements or if amplifiers are needed within the
link to boost the power level at intermediate points. The final step is to perform a
system rise-time analysis to verify that the overall system performance requirements
are met.
The analysis in Sect. 8.1 assumes that the optical power falling on the photodetector is a clearly defined function of time within the statistical nature of the quantum
© 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_8
303
Digital Optical Fiber Links
Abstract The design of a digital optical link involves many interrelated operating
characteristics of the fiber, source, photodetector, and other components in the link.
In carrying out an optical fiber link analysis, several iterations with different device
characteristics may be required before the analysis is completed satisfactorily. The
two basic analyses that usually are carried out to ensure that the desired system
performance can be met are the link power budget and the system rise-time analysis.
In addition to discussing these two analyses, this chapter addresses procedures for
detecting and controlling errors in a digital data stream in order to improve the
reliability of a communication link.
The preceding chapters have presented the fundamental characteristics of the individual building blocks of an optical fiber transmission link. These include the optical
fiber transmission medium, the optical source, and the photodetector and its associated receiver. Now this chapter will examine how these individual parts can be
put together to form a complete optical fiber transmission link. In particular, basic
digital links are addressed in this chapter, and analog links in Chap. 9. More complex
transmission links and networks are examined in Chap. 13.
The first discussion involves the simplest case of a point-to-point link. This
includes considering the transmitted signal format plus examining the components
that are available for a particular application and seeing how these components relate
to the system performance criteria. From a system performance viewpoint, the key
operating criteria include data timing extraction, signal dispersion, power penalties,
and bit error rate. For a given set of components and a given set of system requirements, a power budget analysis then is carried out to determine whether the fiber
optic link meets the attenuation requirements or if amplifiers are needed within the
link to boost the power level at intermediate points. The final step is to perform a
system rise-time analysis to verify that the overall system performance requirements
are met.
The analysis in Sect. 8.1 assumes that the optical power falling on the photodetector is a clearly defined function of time within the statistical nature of the quantum
© 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_8
303