363-206-295
Technical Specifications
Issue 1 December 1997 10-11
‡ The minimum system gain for the DDM-2000 already takes into account aging, temperature, and
manufacturing tolerances as these figures are built into the minimum transmitter power. The
DDM-2000 system gain can, thus, not be directly compared with the DDM-1000 system gain because
the DDM-1000 system gain does not include all of these effects. A similar penalty, called eye margin,
is subtracted from the DDM-1000 loss budget after the value of system gain is determined.
§ Optical path penalty includes effects of dispersion, reflection and jitter that occur on the optical path.
¶ One connector (0.75 dB) on each end is assumed to connect station cable to outside plant.
∗∗ Unallocated margin, or safety margin, is typically specified from 0 dB to 3 dB.
†† If the loss budget is less than 6.0 dB, use low power. Includes a 1.5 dB safety margin.
‡‡ Budget available for both station and transmission cable and splices.
§§ Attenuation and dispersion can be the limiting factors in span length. For OC-3 single-mode fiber
systems, dispersion is not a factor and all applications are attenuation limited. For OC-12 systems,
the maximum distance could be either attenuation limited or dispersion limited. The limits must be
calculated based on both factors and the lesser of the two defines the actual maximum span length.
A rough rule of thumb for attenuation-limited systems is 0.45 dB/km. This estimate includes typical
cable loss (0.4 dB/km) and splice loss (0.2 dB per splice, 11 total splices) associated with single-mode
fiber.
Maximum span length can be calculated more precisely based on particular fiber and splice
characteristics and local engineering rules.
¶¶ Full width at half maximum (FWHM) spectral width.
To Next Page
Loading...
Need help?
General
