ssues that affect systems at the current OC-48/STM-16 (approximately 2.5 Gbps) and OC-192/STM-64 (approximately 10 Gbps) rates. 14,15 Figure 2-30 Minimum detectable Minimum detectable power as a function optical power (dBm) of data rate for APD and PIN photodiodes. 1.56 um operation OC-48 OC-192 1,000 2,500 5,000 10,000 Date rate (Mbps) Chapter 2 Table 2-5 Wavelength 1.3 nm (nom.) or 1.5 nm (dispersion shifted) Typical Optical Line Bit rate 2.5 Gbps (nom.); 10 Gbps being increasingly Parameters introduced Unipolar NRZ Transmitter Power (laser): -3.5 dBm Spectral width (half power): 0.5 nm Receiver sensitivity -32 dBm (for BER = 10-11) Power penalties Dispersion: 0 dB (not limiting) Reflection: 0.5 dB CO losses 2.5 dB Loss margin 3.0 dB Maximum outside plant losses 0.46 dB/km (0.74 dB/mile) Maximum allowable dispersion 3.4 ps/nm/mile Repeater spacing (long haul) 30 miles (more with lower losses) 16 (low-end), 32 (midrange), 80 (high-end) channels each at OC-192 (typical commercially available systems) with spacing in the 100-GHz, 50-GHz, and even the 25-GHz range Table 2-6 OC-48/STM-16 OC-192/STM-64 Typical Link Engi- neering Considera- Moderate OSNR requirement Has 6 dB more OSNR than OC-48 tions Trend to dense channel spacing Trend to dense channel spacing Dispersion not a major Dispersion a major consideration consideration Requires narrow line-width transmitters SMF-28 requires narrow Prechirping transmitters an option line-width transmitters SMF-28 and some NZDSF links require dispersion compensation PMD not an issue PMD an issue over older fiber SMF-28 SMF-28 Limited by OSNR Limited by OSNR, dispersion, and PMD NZDSF NZDSF Balance between OSNR Balance between OSNR and nonlinearities and FWM Typical specs Typical specs 6x25 dB 5X20 dB NZDSF 8X20 dB 5X25 dB SMF-28 with dispersion compensation Next-gen Raman systems extend distance Optics Primer 2.8 Other Technologies This section discusses other optical technologies that play a role in metro access and metro core spaces, as well as in the long haul. SONET/SDH 