Mode Dispersion Compensation Research Articles

Polarization mode dispersion and chromatic dispersion compensation by using a three-stage compensator

A three-stage compensator used for Polarization mode dispersion (PMD) and Chromatic dispersion (CD) compensation is proposed. The compensator is capable of compensating the two components of second-order PMD when no CD exists. Two operating points of compensating second-order PMD have been proposed. Two-stage and three-stage compensators are compared by the outage probability. When CD is introduced, the compensator should retain a quantity of second-order PMD to compensate CD. The outage probability when PMD and CD coexist has been calculated. The results show that a tradeoff must be made in order to compensate CD and PMD at the same time.

High-birefringence linearly chirped grating based optical device for PMD compensation

We propose a novel delay element for polarization mode dispersion (PMD) compensation by employing a tunable high-birefringence linearly chirped grating. The device can adjust differential group delay in a linearly continuous way and its performance is demonstrated by compensating 10-Gb/s signal with the first-order PMD. The tradeoff between PMD compensation capability of the device and the power penalty caused by the chromatic dispersion of the grating has also been studied.

Tunable PMD compensator based on highbirefringence

The simple structure of a tunable polarization mode dispersion (PMD) compensator based on a cantilever beam and a high-birefringence linearly chirped fiber Bragg grating is proposed. A cantilever structure is used to introduce a linear strain gradient on the grating, and we can tune the compensated differential group delay (DGD) at a fixed signal wavelength just by changing the displacement at the free end of the beam. Based on numerical simulations, the performance of the cantilever structure as a PMD compensator is assessed for 10-Gbits/s nonreturn-to-zero transmission systems with a large DGD. With this compensator, a significant improvement of system performance can be achieved in the eye pattern of a received signal.

Impact of relaxed dispersion map and gain ripple on ultra-wideband 10 Gbit/s transmission

The performance of a wide, 53 nm-band fibre-optic transmission system that does not employ slope-matched dispersion-compensation modules or gain-equalisation filters is studied. Despite having a 2 dB maximum transmission penalty resulting from the non-ideal dispersion map, the Raman-based system exhibits a high system margin of at least 5 dB at 1600 km.

Reduction of collision-induced timing jitter in dense wavelength-division multiplexing by the use of periodic-group-delay dispersion compensators.

We show how replacement of a modest fraction of the usual fiber-based dispersion compensation with a periodic-group-delay dispersion-compensating module can result in a drastic reduction in collision-induced timing jitter in dense wavelength-division multiplexing with dispersion-managed solitons. The principal mechanism here is a correspondingly large reduction in the net path over which a pair of colliding pulses interact.

Comparison of engineering scenarios for N x 160 Gb/s WDM transmission systems

We simulate a transmission system at 160-Gb/s bit rate per wavelength and make comparisons between line engineering in order to increase the system reach. We show interesting features of a hybrid scenario combining both inline distributed Raman amplification and lumped erbium amplification before linear higher order mode dispersion-compensating modules.

Low frequency band monitoring method for PMD compensation

A signal monitoring method using a low frequency band is proposed for polarisation mode dispersion (PMD) compensators. By introducing the low frequency band monitoring, a wide range of PMD including differential group delay (DGD) equivalent to a bit period was successfully compensated for the 40 Gbit/s RZ signals.

Ultra-wideband transmission of 1.28 Tbit/s (128 λ×10.7 Gbit/s) over 2000 km using 50% RZ data

High-capacity, long-haul, wavelength-division multiplexed transmission over a 53 nm band centred at 1581 nm, enabled by forward- and backward-propagating Raman pumps and by slope-matched dispersion-compensation modules is demonstrated. Uncorrected bit error rates below 10−10 are exhibited by the 10.7 Gbit/s, 50% return-to-zero signals at 2000 km.

PMD compensator behaviour in presence of noise

It is experimentally demonstrated that noise can have a negative impact on the behaviour of a simple polarisation mode dispersion (PMD) compensator. It is, however, shown that the use of a proper optical filter will cancel the degradation.

Schemes for complete compensation for polarization mode dispersion up to second order

The required structure and elements of polarization mode dispersion (PMD) compensators for complete second-order compensation are investigated by use of a general PMD vector formalism of concatenated PMD elements based on Mueller matrices and Stokes vectors. The investigation shows that two- and three-stage compensators with five independent parameters can compensate for polarization-dependent chromatic dispersion as well as the depolarization component of second-order PMD.

A novel adjustable PMD compensation using sampled Bragg gratings with uniform grating period

We propose a novel solution for linearly tunable polarization mode dispersion (PMD) compensation by sampled Bragg gratings fabricated with uniform-period phase masks. This all-fiber PMD compensation technique is cost-effective and flexible in designing the differential group delay (DGD) profile. Based on numerical simulations, the efficiency of this PMD compensator is assessed for the 10 Gb/s NRZ transmission system with large DGD. With this compensator, a significant improvement can be achieved in the eye pattern of the received signal.

1700 km transmission at 40 Gbit/s with 100 km amplifierspacingenabled by higher-order-mode dispersion compensation

Transmission at 40 Gbit/s over 1700 km of non-zero dispersion fibre with 100 km amplifier spacing is reported for the first time. The demonstration is enabled by an all-fibre higher-order-mode dispersion-compensating module (HOM-DCM) and distributed Raman amplification.

Integrated tunable fiber gratings for dispersion management in high-bit rate systems

Dispersion management is becoming paramount in high-speed wavelength-division-multiplexed lightwave systems, that operate at per-channel rates of 40 Gb/s and higher. The dispersion tolerances, in these systems, are small enough that sources of dispersion variation, that are negligible in slower systems, become critically important to network performance. At these high-bit rates, active dispersion compensation modules may be required to respond dynamically to changes occurring in the network, such as variations in the per-channel power, reconfigurations of the channel's path that are caused by add-drop operations, and environmental changes, such as changes in ambient temperature. We present a comprehensive discussion of an emerging tunable dispersion compensating device, based on thermally actuated fiber gratings. These per-channel devices rely on a distributed on-fiber thin film heater, deposited onto the outer surface of a fiber Bragg grating. Current flowing through the thin film generates resistive heating at rates that are governed by the thickness profile of the metal film. A chirp in the grating is obtained by using a thin-film, whose thickness varies with position along the length of the grating in a prescribed manner; the chirp rate is adjusted by varying the applied current. The paper reviews some of the basic characteristics of these devices and their implementation, in a range of different applications, including the mitigation of power penalties associated with optical power variations. We present detailed analysis of the impact of group-delay ripple and polarization-mode dispersion on systems performance, and present results from systems experiments, that demonstrate the performance of these devices at bit rates of 10, 20, 40 and 160 Gb/s. We also discuss advantages and disadvantages of this technology, and compare to other devices.

16 x 20-Gb/s, 400-km WDM transmission over NZDSF using a slope-compensating fiber-grating module

We demonstrate 16-channel wavelength-division multiplexing transmission over nonzero dispersion-shifted fiber at a per-channel rate of 20 Gb/s. A broad-band dispersion-compensating grating module is used for compensation of dispersion and dispersion slope.