Chromatic Dispersion Monitoring Technique Research Articles

A novel chromatic dispersion monitoring method for 1 024 QAM fiber-optic system based on asynchronous amplitude sampling

A novel chromatic dispersion (CD) monitoring technique based on asynchronous amplitude sampling (AAS) is proposed for a higher modulation format and higher rate system. The dispersion and other impairment factors can be separated with the definition of monitoring parameter M. A 400 Gbit/s 256 quadrature amplitude modulation (QAM) system is built using Optisystem13.0 beta software. Simulations of CD monitoring technique for different bandwidths of sampling Gaussian filter, optical signal to noise ratios (OSNRs) and duty cycles are investigated, and the tolerance is also discussed. Simulation results show that the method can be less affected by noise, and a higher accuracy of 600 ps/(nm·km) can be achieved. The technique supports a wide range of data traffic and enhances operation flexibility of optical networks.

Chromatic Dispersion Monitoring by Synchronizing the Two Sidebands of the Received Optical Signal

In this paper, a new chromatic dispersion (CD) monitoring technique is proposed in optical fiber networks. It is based on detecting the relative group delay between the upper and lower sidebands of the monitored signal (induced by CD) by shifting the two sideband signals a number of times and at every time they are converted to the same frequency, and then they are coupled together with a phase difference of (180o) and the resulting signal power is measured. In one of the shift stages, it obtains minimum power when the time shift equals the relative group delay (i.e. the two sideband signals are synchronized). Therefore, the relative group delay can be detected through searching the minimum output power and the corresponding time shift. The proposed technique is characterized, compared with other monitoring techniques, by good monitoring range with the ability to determine chromatic dispersion sign, high measurement resolution, fixed sensitivity over the whole measurement range, no modification of the transmitter, not affected by polarization mode dispersion (PMD), good tolerance to the amplified spontaneous emission (ASE) noise and the potential to monitor several channels in wavelength division multiplexing (WDM) networks.

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.

Chromatic dispersion monitoring using semiconductor optical amplifier

An all-optical real-time chromatic dispersion (CD) monitoring technique is proposed and demonstrated for 40 Gbit/s differential phase-shifts keying (DPSK) signal, utilizing the cross modulation effects of semiconductor optical amplifier (SOA). The optical power of the output spectral components, which is from the probe’s frequency up to the signal bandwidth, is used for CD monitoring. This technique provides a wide monitoring range with large variation scale. The impacts of the polarization mode dispersion (PMD) and the optical signal-to-noise ratio (OSNR) on the CD monitoring results are theoretically analyzed and then experimentally investigated, showing that they have slight influence on the monitoring results within a certain range. Furthermore, simulated results for quadrature phase shift keying (QPSK) signal at 80 Gbit/s are also demonstrated, indicating that this technique is suitable for advanced modulated format as well.

A novel chromatic dispersion monitoring technique for 16/64-QAM system based on asynchronous amplitude histogram

A novel chromatic dispersion (CD) monitoring technique based on asynchronous amplitude histogram (AAH) for higher order modulation formats is proposed in this paper. Without demodulating the signal, in the monitoring scheme, the received signal is sampled asynchronously, and thus clock information and high-speed sampling units are unnecessary, resulting in low cost and high reliability. Simulations of CD monitoring technique for non-return-to-zero/return-to-zero (NRZ/RZ) 16- and 64-quadrature amplitude modulation (QAM) systems with different optical signal-to-noise ratios (OSNRs) and duty cycles are investigated, and the tolerance of the scheme is also discussed. Simulation results show that the presented CD monitoring technique with high sensitivity can be applied to monitor the residual CD of a transmission link in the next-generation optical networks.

Experimental Demonstration and Analytic Derivation of Chromatic Dispersion Monitoring Technique Based on Clock-frequency Component

In an earlier work, we proposed the chromatic dispersion monitoring technique of non-return to zero (NRZ) signal based on clock-frequency component (CFC) through numerical simulations. However, we have not yet shown any experimental demonstration or analytic derivation of it. In this paper, we show an experimental demonstration and analytic derivation of the proposed chromatic dispersion monitoring technique. We confirm that the experimental results and the analytic results correspond with the simulation results. We also demonstrate that monitoring range and accuracy can be improved by using a simple clock-extraction method.

Chromatic Dispersion Monitoring for NRZ-DPSK System Using Asynchronous Amplitude Histogram Evaluation

We propose and demonstrate a chromatic dispersion (CD) monitoring technique for a nonreturn-to-zero differential phase-shift keying (NRZ-DPSK) signal generated with a Mach-Zehnder modulator at 40 Gb/s by analyzing the waveform overshoot after transmission. Without demodulating the NRZ-DPSK signal, the CD up to 120 ps/nm is monitored experimentally via the amplitude of the overshoot. Furthermore, based on the asynchronous amplitude histogram (AAH) evaluation method, a novel histogram processing method, which is more convenient, is proposed and investigated. Experimental results show that the monitoring scheme for CD is independent of optical signal-to-noise ratio (OSNR) within a certain range. This technique needs neither demodulating the signal nor extracting the synchronous clock, and it can be applied to high-order modulation formats at different bit rates.

Chromatic dispersion monitoring technique using optical asynchronous sampling and double sideband filtering

Abstract This paper introduces a new chromatic dispersion monitoring technique using optical asynchronous sampling and double sideband filtering. We present simulation results that relate chromatic dispersion with the ratio between the maximum amplitude of the signal and the average optical output power, yielding in a method which is power transparent. We also show theoretical investigation and theoretical results that prove the approach used in this paper.

Chromatic Dispersion Monitoring Technique Using Pilot Tone Carried by Broadband Light Source

We propose and demonstrate a simple chromatic dispersion monitoring technique based on the pilot tone generated by a broadband light source (BLS). Previously, the pilot tone has been obtained by directly modulating each transmitter laser with a small sinusoidal current. Thus, for use in the wavelength-division- multiplexed (WDM) network, each transmitter should be modulated with a unique pilot tone. However, we obtain the pilot tone by modulating an additional BLS such as a reflective semiconductor optical amplifier. Thus, there is no need to modulate each transmitter laser. We evaluate the performance of the proposed technique in an 8 times10 Gb/s WDM system. The result shows that, unlike the conventional pilot-tone-based monitoring technique, the performance of this technique is almost insensitive to the polarization-mode dispersion.

Small Signal Transfer Function of Periodically Dispersion-Compensated Optical Link for Intensity Modulated Signals

We present analytical expressions for the transfer function of periodically dispersion compensated optical links within intensity-modulated optical transmission systems. The accuracy of the proposed expressions is confirmed through the simulation based on the split-step Fourier method. With the transfer function, we thoroughly investigate the effects of precompensation and nonzero residual chromatic dispersion (CD) on the performance of periodically dispersion compensated optical links. We also introduce a fast and simple technique to determine the optimum link condition, such as the optimum amount of precompensation and residual CD, and show that there is an optimum monitoring frequency in the CD monitoring technique based on the sub-carrier tone.

All-Optical Chromatic Dispersion Monitoring for Phase-Modulated Signals Utilizing Cross-Phase Modulation in a Highly Nonlinear Fiber

We propose and experimentally demonstrate an all-optical chromatic dispersion (CD) monitoring technique for phase-modulated signals utilizing the cross-phase-modulation effect between the input signal and the inserted continuous-wave probe. The probe's optical spectrum changes with the accumulated CD on the input signal, indicating that the optical power variations can be measured for monitoring. The experimental results show that this technique can monitor up to 120 ps/nm of CD for a 40-Gb/s return-to-zero differential phase-shift keying (RZ-DPSK) transmission system, with the maximum measured optical power increment of 16.5 dB. The applicability of this monitoring technique to higher bit-rate phase-modulated signals, such as 80-Gb/s RZ differential quadrature phase-shift keying and 80-Gb/s polarization-multiplexed RZ-DPSK, is also investigated via simulation.

Chromatic Dispersion Monitoring of CSRZ Signal for Optimum Compensation Using Extracted Clock-Frequency Component

This paper presents a chromatic dispersion monitoring technique using a clock-frequency component for carrier-suppressed return-to-zero (CSRZ) signal. The clock-frequency component is extracted by a clock-extraction (CE) process. To discover which CE methods are most efficient for dispersion monitoring, we evaluate the monitoring performance of each extracted clock signal. We also evaluate the monitoring ability to detect the optimum amount of dispersion compensation when optical nonlinearity exists, since it is more important in nonlinear transmission systems. We demonstrate efficient CE methods of CSRZ signal to monitor chromatic dispersion for optimum compensation in high-speed optical communication systems. Keywords: Carrier-suppressed return-to-zero (CSRZ), clock component, chromatic dispersion monitoring, optical nonlinearity, optimum dispersion compensation.

Chromatic dispersion monitoring in electronic dispersion equalizers using tapped delay lines

We propose a chromatic dispersion monitoring technique by analyzing the tap coefficients in electronic dispersion equalizers using tapped delay lines without needing additional hardware. This technique is robust to varying optical signal-to-noise ratio. The successful chromatic dispersion monitoring is demonstrated by simulation and experiment.

Effective factors of CD monitoring technique based on the narrow-band electrical power detection

Chromatic Dispersion (CD) monitoring technique based on narrow-band electrical power detecting is one of the cost-effective and simple CD monitoring techniques, while the performance of this method is debased by factors such as bandwidth and center frequency of the detected frequency band, self-phase modulation (SPM), light source chirps and optical fiber losses. The CD-electrical power curve is simulated to investigate the effects of the factors above mentioned. Theoretical analysis shows that in single-channeled fiber link, the effect of SPM is small enough (<-0.003%) to be ignored, while the chirps and the losses must be taken into account; the bandwidth of the detected frequency band would better be less than 2πX 1 GHz; the selected central frequency is related to the shape of the original pulse, a central frequency of 12 GHz is chosen in a 40 Gbit/s system, and 5GHz is chosen in a 10 Gbit/s system. A testing system is established. The experimental results agree well with the theoretical analysis.

All-optical chromatic dispersion monitoring of a 40-Gb/s RZ signal by measuring the XPM-generated optical tone power in a highly nonlinear fiber

We experimentally demonstrate an all-optical chromatic dispersion (CD) monitoring technique potential for ultrahigh-speed systems. A monochromatic continuous wave probe is coupled with the tapped-off data signal into a highly nonlinear fiber. An optical tone that is sensitive to CD is generated near the probe wavelength due to the cross-phase modulation effect and is used for CD monitoring. The monitoring window is /spl plusmn/42 ps/nm for 40-Gb/s return-to-zero systems. This monitoring technique is simple and needs no modification at the transmitter.

Improved chromatic dispersion monitoring using single RF monitoring tone

We demonstrate an improved chromatic dispersion monitoring technique using a single RF monitoring tone. Compared to conventional techniques using a single RF monitoring tone, our proposed technique is able to monitor the sign of the residual dispersion and doubles the monitoring range. Our proposed technique utilizes the RF fading caused by chromatic dispersion and a two-detector dispersion monitor setup, where a dispersion offset is inserted before one of the detectors. The observed monitoring error is less than +/-35 ps/nm over a 1300 ps/nm monitoring range. A small power penalty less than 0.5 dB is observed due to the addition of the RF monitoring tone. Our technique is more than twice as accurate as the conventional technique.

PMD and Chirp Effects Suppression in RF Tone-Based Chromatic Dispersion Monitoring

We investigate the effects of polarization-mode dispersion (PMD) and chirp on radio-frequency tone-based chromatic dispersion (CD) monitoring method, and show that the PMD and chirp induce significant CD monitoring errors. We propose a CD monitoring technique to suppress these effects. Experiment results show that the CD monitoring errors induced by PMD and chirp fluctuation are greatly suppressed.

Improved chromatic dispersion monitoring technique

We consider and investigate an improved chromatic dispersion monitoring method using two RF tones with an inserted dispersion offset. This improved technique can be used to monitor both the positive and negative accumulated dispersion caused by optical fibers as well as other optical components in optical networks. We experimentally demonstrate that the monitoring range of the improved technique can be greater than 1150ps/nm and the monitoring sensitivity better than 0.064dB/ps/nm by selecting appropriate RF frequencies and dispersion offsets. Our investigations reveal that the RF modulation index should be greater than 10% but less than 20% so as to acquire a large monitoring range with a small power penalty. We also examine the CD monitoring errors caused by polarization mode dispersion (PMD) and self-phase modulation, and show that the use of a dispersion offset can effectively reduce the PMD-induced monitoring errors.

Chromatic dispersion-monitoring technique based on phase-sensitive detection

A novel chromatic dispersion-monitoring technique is proposed and demonstrated. A path imbalanced interferometer is used to monitor the intensity to phase conversion of a radio-frequency spectral component of a modulated signal. The measurement range of the technique is independent of the data rate and can be tuned by adjusting the path length difference of the interferometer. An unambiguous measurement range of >2300 ps/nm is demonstrated for a 10-GB/s nonreturn-to-zero signal.

Chromatic dispersion monitoring technique employing SOA spectral shift in 40 Gbit/s system

An all-optical online chromatic dispersion monitoring technique in 40Gbit/s system by using of the spectral shift in the semiconductor optical amplifier (SOA) is demonstrated. Spectrum components on the long-wavelength side of 40Gbit/s signal after passing the SOA are extracted for the dispersion monitoring. The range of monitoring can reach ±60ps/nm, and the accuracy of monitoring is less than 5ps/nm.