Polarization Mode Dispersion Monitoring Research Articles

Density-matrix-formalism based scheme for polarization mode dispersion monitoring and compensation in optical fiber communication systems

Density-matrix-formalism based scheme for polarization mode dispersion monitoring and compensation in optical fiber communication systems

Adaptation of transmitting signals over joint aged optical fiber and free space optical network under harsh environments

Over the last two decades, a large amount of optical fiber (OF) cables has been deployed as part of the global communication networks. Both the aging of OFs as well as the need to increase transmission data rates, particularly in the backbone, have become hot topics. We present the study of the aged OF deployment in various optical networks including free space optics (FSO) link as a part of modern optical communication networks. Here, we show extended results obtained using a dedicated OF testbed focusing on the long-term monitoring of polarization mode dispersion (PMD) because of its time-varying nature. The adaptation of polarization multiplexed radio over fiber (RoF) and radio over FSO (RoFSO) systems as well as 10Gbps on-off-keying (OOK) non-return-to-zero (NRZ) intensity modulation with the direct detection system, which is common cost-effective transmission system in passive networks, are demonstrated. Moreover, simulation of 100 and 200Gbps return-to-zero (RZ) differential quadrature phase shift keying (DQPSK) with direct detection is outlined to verify the impact of aged OF network connected with FSO under turbulence conditions. Results reveal more than 6dB of power penalty with the aged OF route for 100Gbps systems. In addition, there is a 0.8dB power penalty due to the strong seasonal induced PMD fluctuations. The influence of scintillations in terms of Rytov variance for the FSO link is also investigated for weak to moderate turbulence. Finally, we derive an expression for the long-term mean PMD value determined over one-month measured frequency response.

Joint CD and PMD monitoring based on a pair of low-bandwidth coherent receivers.

A joint chromatic dispersion (CD) and 1st order polarization mode dispersion (PMD) monitoring technique for both a coherent and a non-coherent single carrier system based on a pair of cost effective low-bandwidth coherent receivers is proposed and experimentally demonstrated. By jointly detecting the narrow band around ± 1/2 baud rate, the CD and PMD can be estimated simultaneously by time domain correlation and Stokes space rotational angle recovery, respectively. The CD estimation range is theoretically infinite and the PMD estimation range is limited to the maximum of 1/2 symbol period. Simulation results show that for a 28 G baud dual-polarization (DP)-16QAM transmission system, with dual 1 GHz coherent receivers, the monitoring error for CD and differential group delay (DGD) is 30 ps/nm and 0.5 ps, respectively. We also experimentally verified it for a 12 GBit/s NRZ-OOK transmission system with a full-bandwidth coherent receiver and two 1 GHz digital filters to simulate dual 1 GHz coherent receivers. The monitoring error for CD and DGD is 60 ps/nm and 1.5 ps, respectively.

Pilot Tone based CD and PMD Monitoring Technique for Photonic Networks

Objectives: This paper aims at evaluation of pilot tone based Chromatic dispersion and Polarization mode dispersion monitoring technique and to find out a suitable solution for simultaneous monitoring of CD and PMD in dynamic optical network. Method: A pilot tone of 2GHz to 8GHz has been send to each channel of a WDM Link for the monitoring of performance degradation of composite signal during the transmission. CD and PMD causes phase shift of LSB and USB of the amplitude modulated pilot tone which results variation of amplitude of the pilot tone. The amplitude of the pilot tome is the parameter by which measurement of different quantities such as optical power, wavelength, OSNR, CD and PMD can be done in a dynamic optical network. Findings: From the various literatures it has been observed that Optical network is switching from static form to dynamic form. Implementation of plug and play devices, adaptive modulation techniques and various dynamic services introduce complexity in photonic network. Due to highly dynamic and heterogeneous nature of optical network, investigation and implementation of appropriate performance monitoring technique is a major challenge for the researchers. This paper presents a pilot tone based method for simultaneous monitoring of CD and PMD. The proposed method is suitable for dynamic optical network and the simulation results shows low frequency pilot tones provides better resolution for both CD and PMD monitoring technique. The simulation result shows that 2GHz pilot tone provides CD measurement range upto 16000ps/nm and PMD DGD value upto 50ps for the tone power variation of -10 to 0dB. Applications: The proposed techniques can be used for simultaneous CD and PMD monitoring of dynamic WDM optical networks.

Simultaneous Monitoring of CD and PMD Using RF Tone Power

We propose and demonstrate a novel method for simultaneous chromatic dispersion (CD) and polarization-mode-dispersion (PMD) monitoring using RF spectrum analysis. In this method, the clock frequency of single sideband of the optical signal is removed by using a narrow bandwidth fiber Bragg grating (FBG) notch filter. After photon detection of the filtered optical signal, the clock tone power of the radio frequency (RF) signal is changed with differential group delay (DGD), which is insensitive to the CD variation. Once DGD value is known, CD value can be estimated from the low-frequency RF tone power after the DGD induced RF power variation is removed. This method enables simultaneous CD and PMD monitoring using detected RF spectrum in the tap line without affecting the received data stream and can be implemented without major modification of the transmitter.

高非线性光纤中并行交叉相位调制的偏振膜色散监测方法

高非线性光纤中并行交叉相位调制的偏振膜色散监测方法

高非线性光纤中并行交叉相位调制的偏振膜色散监测方法

高非线性光纤中并行交叉相位调制的偏振膜色散监测方法

A Pilot-Correlated PMD Monitoring Scheme for Direct Detection Optical OFDM System

A polarization mode dispersion monitoring scheme is proposed and demonstrated for direct-detection optical orthogonal frequency division multiplexing (DDO-OFDM) systems. A pair of data-assisted pilot subcarriers is inserted at two spectral edges of the OFDM signal spectrum. Simple data correlation technique is used to estimate the powers of the pilot subcarriers and thus retrieves the DGD value at the monitoring unit, without the need of demodulation of the pilot subcarriers. Experiments show a DGD monitoring range of 0 to 45 ps in a typical radio-frequency tone-assisted DDO-OFDM system. The robustness of the proposed scheme to optical signal-to-noise ratio and accumulated chromatic dispersion is further experimentally investigated. Besides, simulations and experiments are performed to demonstrate the feasibility of using photodiodes with narrow bandwidth. By inserting one more data-assisted pilot subcarrier, the proposed scheme becomes insensitive to the input angle of the state of polarization. The proposed scheme provides an effective monitoring solution for the optical OFDM signals across intermediate nodes in flexible optical network.

Simultaneous monitoring of first-order polarization mode dispersion and chromatic dispersion based on RF power detection technique

We propose a novel technique for independent and simultaneous monitoring of first-order polarization mode dispersion (PMD) and chromatic dispersion (CD). For PMD monitoring, radio frequency (RF) power is detected after asymmetric filtering by a band-stop filter (BSF). The RF tone power ratio (PR) of the double sideband (DSB) to the single sideband (SSB) signal components is utilized for CD monitoring. We discuss the performance for 80Gb/s NRZ-DQPSK signal by simulation. Simultaneous monitoring of 246.7ps/nm CD with a 22.3dB dynamic range (DR) and 50ps differential group delay (DGD) with a 42.7dB DR can be realized at 10GHz detection band. When only CD is monitored, the detection frequency can be further decreased to 5GHz, where the monitoring range (MR) is 356ps/nm and DR is 30.5dB. The influences of other parameters, such as the BSF offset, the bandwidths of BSF and electrical-band-pass-filter (EBPF), the filter shape, and the modulation rate and format, are investigated in the paper.

CD-insensitive PMD monitoring using electronic domain orthogonal coherent processing for OOK optical link at 40 Gbits/s

We theoretically and experimentally demonstrated the polarization mode dispersion (PMD) monitoring of 40Gbit/s NRZ and RZ links by using a electronic domain orthogonal coherent technique; this method can detect the spectrum phase difference between the fast axes and slow axes. In my experiments, the radio frequency (RF) of local oscillator (LO) is set to 5GHz, the monitoring range is around 0–100 ps, the maximum fluctuation range of measured phase difference is better than 0.05rad for 40Gbit/s NRZ link. This method is independent on data rate for intensity modulation direct detection (IM/DD) links.

SOP and PMD monitoring on deployed aerial optical fibres

State of polarization (SOP) and polarization mode dispersion (PMD) are stochastic in nature due to changes in the properties of the optical fibres and its positions because of both intrinsic and extrinsic perturbations. With 184 PMD values obtained by use of the FTB-5700 single-ended dispersion analyzer, the predicted theoretical Gaussian fit was obtained with a mean of 0.47ps and standard deviation of 0.08ps. This small standard deviation was justification for its accuracy in measuring PMD of aerial optical fibres. A comparison is also made on the accuracy of the GINTY and the FTB-5700 on measurement of PMD of aerial optical fibres with results showing that the latter is more accurate compared to the former. The time scale over which to compensate PMD in aerial optical fibres was determined and it is slightly higher than 400s; the decorrelation time obtained for SOPs on a particular windy and hot day. This is because the changes of the PMD vector are known to be slower than SOP changes.

Optical monitoring of PMD accumulation on a Pol-MUX phase-modulated signal using degree-of-polarization measurements

We experimentally demonstrate a chromatic dispersion insensitive monitoring technique for monitoring of polarization mode dispersion and time misalignment in a 80 Gbit/s polarization-multiplexed return-to-zero differential phase-shift-keying (Pol-MUX RZ-DPSK) signal using a polarimeter and degree-of polarization (DOP) measurements. This technique is modulation format independent (i.e., applicable to both the phase- and amplitude-modulated data) and capable of measuring the fast change of polarization effects caused by vibration or other fast disturbances in the fiber link. We show that the monitored DOP of this signal decreases by 10.8% with differential group delay of 0-12 ps and decreases by 20% with a maximum misalignment of 12.5 ps between two orthogonally polarized RZ-DPSK channels. These measurements are less sensitive to chromatic dispersion of 0-400 ps/nm.

CD-insensitive PMD monitoring based on RF power measurement

We propose and experimentally demonstrate a chromatic dispersion (CD)-insensitive first-order polarization mode dispersion (PMD) monitoring method based on radio-frequency (RF) power measurement. In high-speed (>10-GSym/s) transmission systems, a narrowband fiber Bragg grating (FBG) notch filter filters out the optical components at 10GHz away from the carrier. After square-law detection, the 10-GHz RF tone changes with PMD and is insensitive to CD, which can be used as a PMD monitoring signal. Compared with the monitoring techniques utilizing clock tone, the PMD measurement range is increased from 26.3-ps to 50-ps while the requirement of the bandwidth of photodetector is reduced from 19GHz to 10GHz in 19-Gsym/s systems. It is experimentally shown that this technique is efficient on CD-insensitive first-order PMD monitoring for 38-Gbit/s DQPSK and 57-Gbit/s D8PSK systems.

In-service light path PMD (polarization mode dispersion) monitoring by PMD compensation

We describe a novel method of measuring PMD (polarization mode dispersion) of an in-service DWDM system by PMD compensation. We successfully demonstrate the method in a 1500-km ultra-long haul DWDM test bed. We further verify the feasibility of the method for in-service light path PMD monitoring in a field trial in a revenue-generating route in Verizon Network, and obtain an accurate PMD value without impacting live network traffic. The discrepancy between the measured and expected PMD values is less than 6% for all cases tested.

Optical Performance Monitoring Using Artificial Neural Network Trained With Asynchronous Amplitude Histograms

We propose an optical performance monitoring technique for simultaneous monitoring of optical signal-to-noise ratio (OSNR), chromatic dispersion (CD), and polarization-mode dispersion (PMD) using an artificial neural network trained with asynchronous amplitude histograms (AAHs). Simulations are conducted to demonstrate the technique for both 40-Gb/s return-to-zero differential quadrature phase-shift keying (RZ-DQPSK) and 40-Gb/s noneturn-to-zero 16 quadrature amplitude modulation (16-QAM) systems. The OSNR, CD, and PMD monitoring range and root-mean-square (rms) errors are 10-30 and 0.43 dB, 0-400 and 9.82 ps/nm, and 0-10 and 0.92 ps, respectively, for RZ-DQPSK systems. For 16-QAM system, the monitoring range and rms errors are 10-30 and 0.2 dB, 0-400 and 9.66 ps/nm, and 0-30 and 0.65 ps for OSNR, CD, and PMD, respectively. As the generation of AAH does not require any clock or timing recovery, the proposed technique can serve as a low-cost option to realize in-service multiparameter monitoring for the next-generation transparent optical networks.

CD-insensitive PMD monitoring of a high-speed polarization-multiplexed data channel

We experimentally demonstrate a polarization-mode dispersion (PMD) monitoring technique that is insensitive to chromatic dispersion (CD) utilizing a polarizer and a low-speed detector for an 80-Gb/s polarization-multiplexed return-to-zero differential phase-shift-keying (pol-muxed RZ-DPSK) data channel. Measured RF power increment of 16.2 dB, which is insensitive to 0 approximately 100 ps/nm CD, is measured in the presence of the increasing differential group delay (DGD) from 0 to 12 ps. High-speed components are not required for monitoring the PMD on the pol-muxed data channel, which means that the proposed technique is potentially applicable to the higher speed pol-muxed data channels.

PMD Monitoring in Polarization-Multiplexed Transmission Systems by Spectral Polarimetric Analysis

A polarization-mode dispersion (PMD) monitoring technique tailored for polarization-multiplexed high capacity optical transmission systems is proposed and experimentally demonstrated. First-order PMD is evaluated calculating the vector product of the spectral components of the two state-of-polarization transmitted in the polarization-multiplexed system. The spectral components in each state-of-polarization are resolved by a real-time optical Fourier transformer. The technique is demonstrated measuring first-order PMD in an proof-of-concept experiment implementing an alternate-polarization return-to-zero modulation. The results indicate an improved accuracy over the conventional Poincare-arc measurement method applied to a single polarization. Successful differential group-delay (DGD) measurements have been performed from 0.68 to 30.78 ps with 2.5% maximum relative error. A high degree of independence with the SOP/PSP angle is observed. The technique can be used to generate a feedback signal for PMD compensators in generic polarization-multiplexed transmission systems.

PMD Monitoring in Polarization-Multiplexed Transmission Systems by Spectral Polarimetric Analysis

A polarization-mode dispersion (PMD) monitoring technique tailored for polarization-multiplexed high capacity optical transmission systems is proposed and experimentally demonstrated. First-order PMD is evaluated calculating the vector product of the spectral components of the two state-of-polarization transmitted in the polarization-multiplexed system. The spectral components in each state-of-polarization are resolved by a real-time optical Fourier transformer. The technique is demonstrated measuring first-order PMD in an proof-of-concept experiment implementing an alternate-polarization return-to-zero modulation. The results indicate an improved accuracy over the conventional Poincare-arc measurement method applied to a single polarization. Successful differential group-delay (DGD) measurements have been performed from 0.68 to 30.78 ps with 2.5% maximum relative error. A high degree of independence with the SOP/PSP angle is observed. The technique can be used to generate a feedback signal for PMD compensators in generic polarization-multiplexed transmission systems.

PMD and PDL monitoring of traffic-carrying transatlantic fibre-optic system

For the first time the direct monitoring of polarisation mode dispersion (PMD) and polarisation-dependent loss (PDL) in a traffic-carrying transatlantic fibre-optic system without the requirement of looping-back is reported. The impact of transmitter polarisation scrambling in the measured results is analysed and verified by the measured results.

Real-time polarization mode dispersion monitoring system for a multiple-erbium-doped fiber amplifier, dense wavelength division multiplexing optical fiber transmission by amplified spontaneous emission modulation and acousto-optic tunable fiber scanning techniques

Without interruption or affecting the transmission of ordinary payload channels, we propose a real time polarization mode dispersion (PMD) monitoring system for long-haul, multiple erbium-doped fiber amplifier (EDFA), dense wavelength division multiplexing (DWDM) optical fiber transmission using modulated amplified spontaneous emission (ASE) of one of the EDFAs as the supervisory (SV) signal source. An acousto-optic tunable filter (AOTF) at the receiver side is adopted to scan the spectrum of the transmitted ASE SV signal. Using the fixed-analyzer method, PMDs of different wavelength bands that range from 1545 to 1580 nm of a DWDM fiber-optic communication system can be found by adaptively changing the radio frequency of the AOTF. The resolution and the measuring range of the proposed monitoring system can be significantly improved by cascading the AOTFs at the receiver side.