Volume 35, Issue 3

A detailed circuit model for semiconductor optical amplifier, which incorporates thermal and spectral behavior, is reported. The rate equations of semiconductor optical amplifier form the basis for the equivalent circuit development. The circuit is simulated for static and dynamic conditions and its performance as amplifier, modulator and detector are evaluated. Further, thermal effects on the characteristics of SOA are determined. The SOA performance is studied in the temperature range of 283–343 K and the results are found to agree well with the literature.

This paper mainly does research and analysis on anti-dispersive performance and anti-nonlinear performance for intensity modulation formats such as NRZ, RZ, CS-RZ, DRZ, MD-RZ in 40 Gbit/s high-speed single-channel optical transmission system. It compares the five pattern modulation formats in dispersion tolerance, nonlinear tolerance, and advantages and disadvantages in transmission distance. Anti-nonlinear effect ability of CSRZ, RZ are stronger than that of NRZ code; in the single-channel transmission system, DRZ and improved modulation format MDRZ have better resistance for anti-nonlinear performance, so they are suitable for long-distance transmission. RZ has the minimum dispersion tolerance. NRZ has higher spectrum efficiency than RZ, and thus a better dispersion tolerance. CSRZ code has higher spectral efficiency, higher dispersion tolerance and nonlinear tolerance than RZ code, making it more suitable for long distance transmission.

Incorporating with the supercell method, the simplified versions of triangular-lattice photonic crystal waveguides (PCWGs) are analyzed by plane wave expansion (PWE) method. These simplified PCWGs are composed of one or several layers of rods on both sides of the optical channels. The dispersion curves and the correspondent propagating field distributions are depicted in this paper. Furthermore, the transmission spectra of simplified triangular-lattice PCWGs with different layers of lateral rods are obtained and compared by finite-difference time-domain (FDTD) method.

In this paper, the dominating effect of four wave mixing is analysed with line width of laser source in wave length division multiplexed system. Power of FWM signal is minimum, Q factor maximum and bit error rate is minimized at optimized value of line width at all laser source power.

Passive optical network (PON) is a high bandwidth, economical solution which can provide the necessary bandwidth to end-users. Wavelength division multiplexed passive optical networks (WDM PONs) and time division multiplexed passive optical networks (TDM PONs) are considered as an evolutionary step for next-generation optical access (NGOA) networks. However they fail to provide highest transmission capacity, efficient bandwidth access, and robust dispersion tolerance. Thus future PONs are considered on simpler, efficient and potentially scalable, optical code division multiplexed (OCDM) PONs. This paper compares the performance of existing PONs with OCDM PON to determine a suitable scheme for NGOA networks. Two system parameter are used in this paper: fiber length, and bit rate. Performance analysis using Optisystem shows that; for a sufficient system performance parameters i.e. bit error rate (BER) ≤ 10 −9 , and maximum quality factor (Q) ≥ 6, OCDMA PON efficiently performs upto 50 km with 10 Gbit/s per ONU.

The paper presents design and implementation of a low-cost RAU (Remote Antenna Unit) device. It was designed to work in a hybrid Wi-Fi/optical network based on the IEEE 802.11b/g standard. An unique feature of the device is the possibility of optical power supply.

Grouping the Home Circuits (HCs) with the same source is a critical issue of Labeled Optical Burst Switching with Home Circuit (LOBS-HC). To maximize the wavelength utilization in LOBS-HC ring networks, an HC grouping and wavelength assignment scheme, called Longest Path Matching and Graph Coloring (LPMGC), is proposed. LPMGC consists of two phases: grouping and wavelength assignment. First, a heuristic algorithm, named Longest Path Matching (LPM), is proposed to group the HCs according to the longest common path matching between HCs and to make each group as large as possible. And then, Graph Coloring (GC) is introduced to assign wavelengths for HC groups. The numerical results show that the proposed scheme performances better than Complementary HC Assignment (CHA) and some other heuristics in both unidirectional and bidirectional LOBS-HC ring networks in terms of wavelength utilization.

In this paper, we analyze the sensitivities of coherent optical receivers and microwave receivers. We derive theoretical limits of signal-to-noise ratio and bit error rate. By applying a generic approach to a broad range of receivers, we can compare their performance directly. Other publications have considered some of these receivers. However, their diverse nature obscures the big picture. Using our results as a unifying platform, previous publications can be compared and discrepancies between them identified.

Hybrid wavelength-division multiplexed/time-division multiplexed passive optical access networks (WDM/TDM-PONs) combine the advance features of both WDM and TDM PONs to provide a cost-effective access network solution. We demonstrate and analyze the transmission performances and power budget issues of a colorless hybrid WDM/TDM-PON scheme. A 10-Gb/s downstream differential phase shift keying (DPSK) and remodulated upstream on/off keying (OOK) data signals are transmitted over 25 km standard single mode fiber. Simulation results show error free transmission having adequate power margins in both downstream and upstream transmission, which prove the applicability of the proposed scheme to future passive optical access networks. The power budget confines both the PON splitting ratio and the distance between the Optical Line Terminal (OLT) and Optical Network Unit (ONU).

We have proposed and demonstrated a novel architecture of cost effective bidirectional wavelength division multiplexed passive optical network (WDM-PON) system based on reflective semiconductor optical amplifier (RSOA), using optical carrier suppression (OCS) method. RSOA is employed at the user end to remodulate the downstream lightwave for uplink transmission. The OCS scheme is used to reduce the power loss of the signal during the transmission. A data rate of 10 Gbit/s is successfully transmitted over a single mode fiber (SMF) of more than 40 km length. The outstanding transmission performances at uplink and downlink have been observed by measuring the high Q factor and the sufficient low bit error rate (BER) at the BER tester.

Advanced modulation schemes play a vital role for RoF communication system for different channels. Keeping into view the same, in this paper a DQPSK (Differential Quadrature Phase Shift Keying) based radio over fiber system is proposed. Appropriate value of FWHM is also concluded for faithful communication.

A new bandwidth allocation algorithm was presented by combining merits of the IPACT algorithm and the cyclic DBA algorithm based on the DBA algorithm for ONU's sleep mode. Simulation results indicate that compared with the normal mode ONU, the ONU's sleep mode can save about 74% of energy. The new algorithm has a smaller average packet delay and queue length in the upstream direction. While in the downstream direction, the average packet delay of the new algorithm is less than polling cycle T cycle and the average queue length is less than the product of T cycle and the maximum link rate. The new algorithm achieves a better compromise between energy-saving and ensuring quality of service.

The transmission performance of single sideband (SSB) radio over fiber (RoF) system is evaluated through tuning the modulation index of Mach-Zehnder modulator, two different data modulation schemes and the influence of fiber dispersion are considered. The quantitative simulation results validate that there exist an optimum modulation index, and the system performance could be improved if the data signal is modulated on only optical carrier or sidebands.