Hua Jiao

Study of system performance in a 107-km dispersion-managed recirculating loop due to polarization effects

We investigate the polarization evolution for both signal and noise in two 107-km recirculating loops with polarization-dependent loss per round-trip of 0.35 dB and less than 0.1 dB, respectively. When the system is optimized, in the first case, both signal and noise are polarized, while in the second case, the signal tends to depolarize due to the noise. We experimentally measured and theoretically simulated the Q factor distribution, which is far from what is expected for straight-line systems, after 5000 km in the second case. We also suggest a simple method for obtaining the same Q distribution in recirculating loop experiments as expected in straight-line experiments.

System performance variations due to partially polarized noise in a receiver

We systematically investigate effects of partially polarized noise in a receiver. We introduce a relationship between the Q factor and the signal-to-noise ratio (SNR) that accounts for effects of partially polarized noise. We derive an expression for the distribution of the Q factor for a fixed SNR, and we validate our results by comparison to back-to-back experiments. We show that the system performance varies depending on the angle between the Stokes vectors of the signal and the noise as well as the degree-of-polarization of the noise. Highly polarized noise will cause a larger variation of the system performance.

An experimental demonstration of a soft-failure approach to PMD mitigation in an installed optical link.

We present a field-trial implementation of the soft-failure approach to polarization-mode dispersion (PMD) impairment mitigation, in which information about the PMD of the installed link is utilized by our modified control plane software to make decisions on data routing over available links. This allows us to maintain loss-free end-to-end data service, even at high PMD levels.

Quantitative experimental study of intra-channel nonlinear timing jitter in a 10 Gb/s terrestrial WDM return-to-zero system

Using a recirculating loop, we measure nonlinearly-induced timing jitter at different transmission distances for different amounts of pre-compensation. Within each sub-band, we achieve error-free transmission using the same pre-compensation for all channels at all distances up to 5000 km.

Effects of partially polarized noise in a receiver

We compare back-to-back experiments to an accurate receiver model and an analytical formula for the Q-factor distribution. We show that even for a fixed SNR, partially polarized noise can cause a large variation in system performance.

Receiver Model for Depolarized Signal Due to Polarization-Mode Dispersion and Partially Polarized Noise Due to Polarization-Dependent Loss in an Optical Fiber Communication System

We systematically investigate the combined effect on the system performance in an optical fiber communication system of a signal that is depolarized due to polarization-mode dispersion (PMD) and noise that is partially polarized due to polarization-dependent loss. We derive a formula for the variance of the electric current of the signal due to the signal-noise beating between a depolarized signal and partially polarized noise. We validate this theoretical formula by comparing the Q -factor calculated using the theory to results obtained from Monte Carlo simulations and experiments. We show that the system performance strongly depends on the power-splitting ratio, the degree of polarization of the noise, and the angle between the states of polarization of the signal and the polarized part of the noise. Although the theoretical formula is derived assuming that the optical fiber only has first-order PMD, we show that for arbitrary fiber, this formula still produces a reliable estimate of the Q-factor provided that the second-order PMD is on the order of 300 ps2 or less.

Probability density functions of rotations in loop-synchronous polarization scrambling for recirculating loop experiments

The performance in a recirculating loop with a loop-synchronous polarization scrambler is independent of the choice of probability density function (pdf) for the rotations in the polarization scrambler, unless the pdf is strongly biased

Noise effect on the measurement of polarization-mode dispersion in a system with polarization-dependent loss using a generalized Poincare sphere method

We simulate the measurement statistics of differential group delay and differential attenuation slope in a long-haul fiber communication system using a generalized Poincare sphere method and found them to be sensitive to Stokes noise.

Effects of polarization dependent loss and polarization mode dispersion in recirculating loops

This study demonstrates detailed experiments and modeling on the effects of polarization dependent loss (PDL) and polarization mode dispersion (PMD) in recirculating loops. Experimental results and modeling show that the Q distribution is affected by noise which is partially polarized due to the PDL. Due to polarization dependence of the gain (PDG) in erbium doped finer amplifiers (EDFA), single channel experiments require input scrambling to eliminate this effect. Due to gain saturation in an EDFA chain the input scrambling rate can be chosen to eliminate unwanted amplitude modulation.

Variation of system performance in a 107 km dispersion managed recirculating loop due to polarization effects

Summary form only given. Polarization effects can have a severe impact on the performance of long-haul multigigabit light wave system using erbium-doped fiber amplifiers (EDFAs). Recirculating loops are commonly used as experimental models for studying long-haul transmission systems, making it important to understand the polarization effects inside these loops. Our prior study shows, experimentally and theoretically, that in short loops both the signal and noise become highly polarized as a function of propagation distance when the PDL (polarization dependent loss) is large. in the present research we lowered the PDL of our loop to a point where the PDG (polarization dependent gain) becomes important. We then measured the Q factor distribution of our loop at 5000 km and compared the measured result with theoretical calculation using a reduced model. We were able to show by measurement and subsequent analysis that even after randomizing the polarization state in the loop the Q factor distribution was far from what is expected for a randomized straight-fine system. In addition we are able to show simplified methods for realizing in recirculating loops a more randomized Q distribution appropriate for emulating straightline experiments.