S. Hinz

Crosstalk detection schemes for polarization division multiplex transmission

Polarization division multiplex (PolDM) is a bandwidth-efficient and sensitive modulation format suitable for upgrading bandwidth-limited trunk lines. We show how control signals for polarization demultiplex can be obtained efficiently. For interleaved return-to-zero (RZ) signals, incoherent crosstalk has to be detected and minimized. In other cases, in particular for non-return-to-zero (NRZ) signals, coherent crosstalk senses penalties much better and should be detected instead. NRZ transmission experiments with either scheme are presented at a data rate of 2/spl times/10 Gb/s, with endless polarization tracking. Polarization mode dispersion (PMD) tolerance is also assessed.

Polarization mode dispersion detected by arrival time measurement of polarization-scrambled light

Polarization mode dispersion (PMD) limits optical fiber capacity. PMD compensators usually minimize the associated eye closure. This measure scales with the square of the differential group delay (DGD) and makes it difficult to detect low DGDs. However, light with a low-speed polarization modulation suffers arrival time variations, in the presence of PMD, that are proportional to the DGD. These are detected by integrating the voltage-controlled oscillator (VCO) input signal of the clock recovery phase-locked loop (PLL). This novel method has been demonstrated for 40 Gb/s nonreturn-to-zero (NRZ) and for 2/spl times/40 Gb/s return-to-zero (RZ) polarization division multiplex transmission. PMD detection sensitivities range between 2 ps and 84 fs.

Polarization mode dispersion compensation at 20 Gb/s with a compact distributed equalizer in LiNbO/sub 3/

PMD of existing fibers impairs transmission at rates greater than 10 Gb/s. We present a 43 ps PMD compensator in X-cut, /spl gamma/-propagation LiNbO/sub 3/ with cascaded TE-TM converters and demonstrate successful operation at 20 Gb/s.

PMD tolerance of polarization division multiplex transmission using return-to-zero coding

Polarization division multiplex (PolDM) doubles the data rate in existing trunk lines without need for additional optical bandwidth. In the presence of dispersion compensation, polarization mode dispersion (PMD) limits the achievable transmission length. PMD tolerance of standard binary intensity modulation or non-return-to-zero coding has already been published. Recently, the return-to-zero (RZ) transmission format has become of more interest; therefore we assess the PMD tolerance of PolDM by numerical simulations and a transmission experiment. For a given total data rate per wavelength PolDM supports at least as much differential group delay as standard binary intensity modulation. So, PolDM is an attractive multilevel modulation scheme to solve capacity problems with low additional effort.

Fiber-based distributed PMD compensation at 20 Gb/s

Ideal equalization of polarization mode dispersion (PMD) can be expected from an equalizer that mirrors the differential group delay profile of a transmission line. We successfully operate a (polarisation mode fibre) PMD-based 77 ps compensator at 20 Gb/s.

150 fs online PMD detection within 5 /spl mu/s

Light with a low-speed polarization modulation suffers arrival time variations due to PMD (polarization-mode dispersion), detectable by integration of the VCO (voltage-controlled oscillator) input signal in the clock recovery PLL (phase locked loops). This is demonstrated in 40 Gbit/s NRZ (non RZ) and 2/spl times/40 Gbit/s RZ (return-to-zero) polarization multiplex transmission experiments.

10-Gb/s PMD compensation using ferroelectric liquid crystals and several PMD penalty signals

Polarization mode dispersion (PMD) hampers development of greater than or equal to 10 Gb/s trunk lines but can be compensated by endless polarization controllers and birefringent fiber. We demonstrate automatic 10 Gb/s PMD compensation using three deformed-helix ferroelectric liquid crystal cells.