Considerations for Single-Mode Fiber Systems

The intrinsic low-dispersion property of single-mode fibers makes them attractive for high-capacity, long-haul lightwave systems,1'2 especially in the wavelength region between 1.1 and 1.7 jum, where low attenuation (less than 1 dB) has been demonstrated.' Minimum dispersion can be achieved over a range of wavelengths above 1.3 /im by controlling Ge-doping density and core size.4"'' Low dispersion over a wide range of wavelengths can be achieved by introducing a certain amount of waveguide dispersion. '8 As in any communication system, there are three basic origins of system-performance limitations and degradations: (i) sources, (ii) media, and (iii) receivers. Some limitations, such as receiver sensitivity and source-output power, are determined by a single component. However, many other performance limitations and degradations are caused by the interaction of two components. Laser diodes as sources have several characteristics that result in 1919 Table I -- D e g r a d a t i o n f a c t o r s of laser d i o d e s Characteristics of Laser Center wavelength Manufacturing variation ±3 nm Temperature variation 0.5 nm/°C Mode skipping (jumps) 6 ~ 10 AA Spectrum (halfrms width) Half rms width 2 - 4 nm Spectrum broadening Mode partition (0 ^ k S 1) Quantum noise Transverse mode fluctuation Spectrum noise Self-pulsing 1 ~ 2 GHz Related Fiber Characteristics Degradation Effects to System Bandwidth (with fiber dispersion) Bandwidth (with fiber dispersion) Burst error Chromatic dispersion