M. T. Al-Qdah

System performance optimization in SCM-WDM passive optical networks in the presence of XPM and GVD

The authors investigate semi-analytically the optimized system performance limitation in an SCM-WDM passive optical network (PON) in the presence of cross phase modulation (XPM) and group velocity dispersion (GVD). A general expression for electrical average crosstalk noise power due to XPM and GVD was derived to measure the system performance for increasing number of WDM channels. Using the expression, we show that XPM and GVD causes crosstalk in the system and imposes a power penalty as the WDM channels increases for a given channel spacing and modulating frequency. These results are extended to show that the system can be optimized to achieve a minimum BER of 10-9 by controlling the channel spacing and modulating frequency as the number of WDM channels increases.

Chromatic dispersion power penalties in orthogonal subcarrier--optical tandem single sideband systems

This paper deals with power penalties in Optical Tandem Single Sideband system using orthogonal subcarriers due to chromatic dispersion. The upper and lower sideband orthogonality is affected by chromatic dispersion. This phase imbalance causes degradation of quadrature demodulation performance. The effect is demonstrated by a mathematical model and verified by simulation results.

A new optical modulator chirp measurement technique using differential frequency beating

A new method to measure the modulator chirp parameter is proposed. This method will be performed in two steps. In the first step, the frequency separation between two optical signals passing through a phase conjugator is changed. This produces a resonance reference frequency as a result of the accumulated fibre chromatic dispersion (CD). In the second step, a RF modulated signal passes though the same length of fibre as in the first step. A second resonance frequency is produced as a result of fibre CD and modulator chirp. The difference between the two resonance frequencies is used to measure the modulator chirp. The new method successfully achieves a wide measurement range with low modulating frequencies.

The effects of drive level errors on optical SSB system performance

This paper presents a system performance analysis of an optical single sideband system (OSSB) when drive level errors occur in the modulating signal driving the dual arm Mach-Zehnder modulator (MZM). The performance is evaluated in terms of the optical sideband suppression, frequency response and power penalty measurements. Experiments are carried out and a mathematical model of the OSSB system incorporating the drive level error is developed. The theoretical and experimental results suggest that the drive level error leads to reduced system performance as a result of poor received subcarrier power. The overall frequency response of the system, which is affected by drive level errors, accumulated CD and subcarrier frequency, has a direct influence over the power penalty. However, reduction in power penalty slope is observed at peaks of the OSSB frequency response.

Semi-analytical performance analysis of an SCM-WDM PON in the presence of XPM and GVD

The authors analyze semi-analytically the performance in an SCM-WDM passive optical network (PON) in the presence of cross phase modulation (XPM) and Group Velocity Dispersion (GVD). A general expression for electrical average noise power and electrical crosstalk level due to XPM and GVD was derived to measure the system performance for N number of WDM channels. Using the expression, we show that XPM and GVD causes crosstalk in the system and imposes a power penalty as the number of WDM channels increases for a given channel spacing and modulating frequency.

Employing dispersion-flattened fiber for chromatic dispersion measurement

A new technique for measuring the accumulated chromatic dispersion (CD) in single-mode fiber (SMF) is presented. The technique uses the ratio of the beating power between pump and probe signals and the beating power between probe signal and the four-wave mixing (FWM) conjugated signal. The technique is successfully demonstrated using dispersion-flattened fiber (DFF) as a phase conjugator to achieve a 20-dB relative power variation as a result of up to 1000 ps/nm accumulated CD change.

Chromatic dispersion penalties in orthogonal subcarrier - optical tandem sideband systems (OTSSB)

This paper deals with dispersion penalties in an optical tandem single sideband system using orthogonal subcarriers. A mathematical model demonstrates the phase imbalance of the upper and lower sideband caused by chromatic dispersion and verified by simulations. The transmission over 10 km of single mode fiber (SMF) using different subcarrier frequencies shows higher penalties for higher subcarrier frequencies.

Chromatic dispersion measurement using optical beating null frequency

A new technique for measuring the accumulated chromatic dispersion in single-mode fibers is presented. The proposed simple and tunable technique uses the null frequency of the optical beating signal between pump, probe, and four-wave-mixing conjugated signals as the pump and probe frequency separation is changed. The null frequency of the optical beating signals varies with the accumulated chromatic disper- sion in the single mode fiber. A full mathematical model of the measure- ment technique is developed and is supported by experimental results. The technique is successfully demonstrated experimentally using a semiconductor optical amplifier as a phase conjugator to achieve a null frequency variation of 1.2 GHz for a difference of 960-ps/nm accumu- lated chromatic dispersion.

Subcarrier multiple access system using a single optical source to suppress optical beat interference

The authors propose, design and analyze a Subcarrier Multiple Access system using a single optical source to suppress Optical Beat Interference (OBI). A mathematical model is developed and an experiment is carried out to study the performance of the system. The experimental results are in agreement with the mathematical model, which show an OBI free transmission.