Fiber Optics

INTRODUCTION Optical fibers were first envisioned as optical elements in the early 1960s. It was perhaps those scientists well-acquainted with the microscopic structure of the insect eye who realized that an appropriate bundle of optical waveguides could be made to transfer an image and the first application of optical fibers to imaging was conceived. It […]

Optical Fibers and Fiber-Optic Communications Part 2

Normalized Variables in Fiber Description The propagation constant and dispersion of guided modes in optical fibers can be conveniently expressed in the form of normalized variables. Two common engineering problems are the determination of mode content and the computation of total dispersion. For example, commonly available single-mode fibers are designed for a wavelength range of […]

Optical Fibers and Fiber-Optic Communications Part 3

Reliability Assessment The reliability of an optical fiber is of paramount importance in communications applications—long links represent large investments and require high reliability. There will, of course, always be unforeseen reliability problems. Perhaps the most famous such example was the fiber cable design on the first transatlantic link—the designers had not quite appreciated the Atlantic […]

Optical Fibers and Fiber-Optic Communications Part 4

Point-to-Point Links The simplest optical communications system is the single-channel (no optical multiplexing) point-to-point digital link. As illustrated in Fig. 16, it consists of a diode laser (with associated driver circuitry and temperature control), optical fiber (with associated splices, connectors, and supporting material), and a detector (with appropriate electronics for signal processing and regeneration). The […]

Optical Fibers and Fiber-Optic Communications Part 5

Advanced Transmission Techniques The optical bandwidth available in either of the low-loss transmission windows of the fiber exceeds 1013 Hz. Two ways of taking full advantage of this bandwidth are through the use of ultrashort pulse transmission combined with time-division multiplexing or the use of wavelength/frequency-division multiplexing. Either technique can overcome the limits imposed by […]

Optical Fibers and Fiber-Optic Communications Part 6

NONLINEAR OPTICAL PROPERTIES OF FIBERS A selection of these are included in "Further Reading" at the end of this topic. We will content ourselves with an overview of the subject, and consider nonlinear effects which are most important in either limiting or enhancing the performance of fibers. To date, most of the applications of nonlinear […]

Optical Fiber Communication Technology and System Overview Part 1

INTRODUCTION Basic elements of an optical fiber communication system include the transmitter [laser or light-emitting diode (LED)], fiber (multimode, single-mode, or dispersion-shifted), and the receiver [positive-intrinsic-negative (PIN) diode and avalanche photodetector (APD) detectors, coherent detectors, optical preamplifiers, receiver electronics]. Receiver sensitivities of digital systems are compared on the basis of the number of photons per […]

Optical Fiber Communication Technology and System Overview Part 2

BIT RATE AND DISTANCE LIMITS Bit rate and distance limitations of digital links are determined by loss and dispersion limitations. The following example is used to illustrate the calculation of the maximum distance for a given bit rate. Consider a 2.5-Gbit/s system at a wavelength of 1550 nm. Assume an average transmitter power of 0 […]

Nonlinear Effects in Optical Fibers Part 1

Fiber nonlinearities are important in optical communications, both as useful attributes and as characteristics to be avoided. They must be considered when designing long-range high-data-rate systems that involve high optical power levels and in which signals at multiple wavelengths are transmitted. The consequences of nonlinear transmission can include (1) the generation of additional signal bandwidth […]

Nonlinear Effects in Optical Fibers Part 2

STIMULATED BRILLOUIN SCATTERING The stimulated Brillouin scattering process (SBS) involves the input of a single intense optical wave at frequency m2, which initiates a copropagating acoustic wave at frequency op. The acoustic wave is manifested as a traveling index grating in the fiber, which back-diffracts a portion of the original input. The backward (Stokes) wave […]