An overview over applications of the different fibers types used in optical networks, current market opportunities and research trend in the development of optical fiber will be presented. India's first dense wavelength-division-multiplexing (DWDM) long-haul coherent transmission performance will be presented. The DWDM network system consists of 80ch×128 Gbit/s coherent PDM-QPSK channels spaced at 50 GHz over 23 spans of 80 km standard Sterlite OH-LITE G652.D fiber. The loss of each span were compensated with a variable gain erbium-doped fiber amplifier (EDFA). A dynamic gain equalizer (DGE) was used after every 6 spans to compensate gain ripple of the EDFAs. No dispersion compensation was used in the link. The bit-error ratio (BER) of various channels across C-band was measured to be better than the pre-SD-FEC limit of 2.0×10-2 (with a 20% overhead) after 1840 km transmission using a launch power of 0 dBm/ch.