W.S. Lee

Field evaluation of an optical PMD compensator using an installed 10 Gbit/s system

We report, for the first time, results correlating PMD compensation performance to system instantaneous differential group delay (DGD) over installed fibre. We also report accurate replication of the installed fibre PMD conditions in a laboratory providing accelerated PMD exploration.

40-Gbit/s TDM transmission over 160 km (2/spl times/80 km) of standard nondispersion-shifted fiber

It is anticipated that fiber chromatic dispersion is one of the key performance-limiting factors in the next generation high-speed time-division multiplexing (TDM) systems operating at 40 Gbit/s. To date, much effort has been focused on the issue of signal propagation using dispersion-shifted fiber (DSF). In reality, the existing fiber base is predominantly nondispersion-shifted fiber (NDSF) exhibiting dispersion values between 15 and 17 ps/nm/km with respect to the erbium-doped fiber amplifier wavelength window. Some ways of compensating this level of dispersion will be necessary. In this paper, we report the TDM transmission of 40-Gbit/s data on these high-dispersion-standard NDSF. The optimum position of the dispersion-compensating fiber was evaluated in single- and multi-span configurations. System results for operation up to two spans of NDSF are presented. Comparison with system simulation is also be made.

Eight-channel 40 Gb/s RZ transmission over four 80 km spans (328 km) of NDSF with a net dispersion tolerance in excess of 180 ps/nm

We report experimental results on simultaneous transmission and dispersion compensation of eight wavelengths at 200 GHz channel spacing over 328 km of standard NDSF at 40 Gb/s, using GaAs HBT multiplexer and negative slope dispersion compensators. Individual channel Q values between 7.6 to 8.8 were achieved.

Widely tunable twin fiber grating dispersion compensator for 80 Gbit/s

The dispersion tolerance of an 80 Gbit/s system is broadened 27-fold, from 32.7 ps/nm to 884.9 ps/nm, using an adjustable dispersion compensator with novel grating design. This is the largest reported broadening of any system.

40 Gbit/s high performance filtering for DWDM networks employing dispersion-free fibre Bragg gratings

Near penalty-free filtering with high bandwidth utilisation at 40 Gbit/s is demonstrated for the first time using fibre Bragg gratings. When tested in a typical add-drop configuration, a 100 GHz dispersion-free Bragg grating show Q-penalty variations of less than 1.0 dBQ over most of the 1 dB reflection-bandwidth, confirming its superior performance.

Polarisation-channel-interleaved carrier-suppressed RZ ETDM/DWDM transmission at 40 Gbit/s with 0.8 bit/s/Hz spectral efficiency

We report experimental results of 8/spl times/40 Gbit/s polarization-channel-interleaved carrier-suppressed RZ transmission over 2/spl times/160 km NDSF, with 0.8 bit/s/Hz spectral efficiency. Average system linear Q of 6.5 (2/sup 31/-1 PRBS) and tolerance of at least 50% degradation in orthogonality were demonstrated.

All-Raman unrepeatered transmission of 1.28 Tbit/s (32/spl times/40 Gbit/s) over 240 km conventional 80-/spl mu/m/sup 2/ NDSF employing bi-directional pumping

A total of 32 channels of 40 Gbit/s CS-RZ ETDM signals have been successfully transmitted over an unrepeatered span of 240 km conventional 80-/spl mu/m/sup 2/ NDSF employing all-Raman amplification and bi-directional pumping. No large-effective-area fibres, hybrid transmission lines, or intraspan remotely pumped EDFAs were used. Up to 65 dB span loss, out of a total span loss of 93.8 dB, has been compensated. Individual channel Q-factors between 12.5 dB and 14.5 dB, at a PRBS pattern length of 2/sup 31/-1, were achieved without using FEC. Bi-directional pumping with pump laser RINs around -140 dB/Hz has allowed an average OSNR improvement by 6 dB in the transmission fibre, compared to either counter-pumping or co-pumping alone. This highlights the prospect of possible performance enhancement in high bit rate multiple long-span systems by bi-directionally pumped distributed Raman amplification, as compared to counter-pumping only, or unrepeatered transmissions with additional adoption of fibre effective area management and remote pumping.

Experimental comparison of dispersion-managed fiber types in a 16-channel 40 Gb/s 500 km (6 /spl times/ 84.5 km) Raman-assisted transmission link

Summary form only given. The concept of a dispersion-managed transmission span consisting of a positive (PDF) and a negative dispersion fiber (NDF) section offers the promise of highly accurate in-line chromatic dispersion control. Our experimental results confirmed that the composite PDF-NDF-PDF span configuration yielded superior Q performance and tolerance to nonlinearity over a broad range of signal launch power and Raman gain, compared to the simpler PDF-NDF arrangement. This enhanced span configuration, with the small area NDF inserted between two large area PDFs, is better suited for long haul applications where nonlinearity tolerance, dispersion management and reduced PMD are critical factors.

Experimental comparison of all-Raman vs. Raman/EDFA hybrid amplification with 40 Gb/s-based ETDM/DWDM transmissions over 400 km TW-RS fibre

Summary form only given. A 400 km TW-RS fibre system with 16 channels of 40 Gbit/s CS-RZ ETDM signals has been used to experimentally compare the relative merits of all Raman and Raman/EDFA hybrid amplification. In the cases of counter-pumped 10 /spl times/ 40 km and 5 /spl times/ 80 km spans, all Raman distributed amplification has allowed best transmission performance, compared to Raman/EDFA hybrid amplification. All Raman transmission yielded up to 1.3 dB system Q improvement in the 40 and 80 km span length systems, compared to systems without Raman gain. The MPI impairment associated with the double Rayleigh scattering effect in all-Raman counter-pumped long span systems, was significantly reduced in an experimental demonstration over 1 /spl times/ 160 + 2 /spl times/ 120 km TW-RS fibre, by employing multi-span bidirectionally pumped all Raman amplification.

16-channel 40 Gb/s carrier-suppressed RZ ETDM/DWDM transmission over 720 km NDSF without polarisation channel interleaving

We report experimental and simulation results on transmission. and simultaneous dispersion-compensation of 16/spl times/40 Gb/s carrier-suppressed RZ ETDM signals with 0.4 bit/s/Hz spectral-efficiency over 6/spl times/120 km NDSF. Q-factors between 16.3 and 17.7 dB were achieved at 2/sup 31/-1 pattern length without FEC or polarisation interleaving.