Volume 34, Issue 3

The behaviour of the eigenfunctions and eigenvalues, that are used to describe the eigenfunction expansion of the receiver decision variable of an optical direct detection differential phase-shift keying (DPSK) system with optical amplification, is analysed for various receiver configurations, and their impact on system performance is investigated. In particular, special attention is given to the ideal receiver, based on an ideal optical filter and an electrical integrate-and-dump filter, to the Gaussian receiver, based on Gaussian shaped filters for both the optical and electrical filters, and to a receiver configuration based on a Lorentzian optical filter and an electrical RC filter.

We demonstrate single Mach-Zehnder Modulation (MZM) format with hybrid Raman and Erbium Doped Fiber Amplifier (EDFA) configuration to generate Return to Zero Differential Phase Shift Keying (RZ-DPSK) modulation signal that can compensate dispersion impairment to investigate transmission distance in the 48 × 40 Gbit/s Dense Wavelength Division Multiplexing (DWDM) system. The proposed 48 × 40 Gbit/s DWDM system system successfully employs single MZM RZ-DPSK modulation format to reduce modulation complex configuration with employs hybrid Raman Amplifier and Erbium Doped Fiber Amplifier to promote the power signal and using Larger Effective Area Fiber (LEAF) and Reverse Dispersion Fiber (RDF) in 28 spans over 3360 km ultra-long haul fiber transmission successfully.

A Cascaded chirp fiber Bragg grating has been theoretical analyzed by using coupled mode equations and transfer matrix method. As a dispersion compensator, a wide bandwidth, big dispersion value, and low delay ripple cascaded chirp fiber Bragg grating is designed for a 200 km 8 × 160 Gbit/s high speed quasi-linear optical transmission system. The system Q value of 7.15∼8.74 demonstrates the success of the design of the cascaded chirp fiber Bragg grating.

We propose and demonstrate simultaneous demultiplexing and demodulation of wave length division multiplexed (WDM) return-to-zero differential phase-shift keying (RZ-DPSK) signal by a standard Arrayed Waveguide Gratings (AWG) at 10 Gbit/s data rate using ITU grid of 100 GHz channel spacing. Simulation results show error free transmission in a distance of 25 km with negligible power penalty and improved receiver sensitivity. The propose scheme is cost effective in term of component counts, hence reduces the deployment cost significantly.

Employing the series expression for the fundamental modal field of dispersion-shifted trapezoidal and dispersion-flattened graded and step W fibers, we present simple but accurate analytical expressions for Petermann I and II spot sizes of such kind of fibers. Choosing some typical dispersion-shifted trapezoidal and dispersion-flattened graded and step W fibers as examples, we show that our estimations match excellently with the exact numerical results. The evaluation of the concerned propagation parameters by our formalism needs very little computations. This accurate but simple formalism will benefit the system engineers working in the field of all optical technology.

In pulsed fiber laser using Q-switching or mode locking techniques, the choice of the different components and the management of linear and non linear parameters of the cavity, play a paramount role in the generation of stable ultra short pulses with high peak powers and low widths. In this paper, we focus on the operating process of mode locked fiber lasers especially passively and hybrid type Eight Fiber Lasers (8FLs). By modeling the light propagation within the two cavities, we describe the whole operating process of ultra short pulses generation. The interaction between the mode locking mechanism and nonlinear effects in fiber laser is also illustrated. We demonstrate enhancing non linear effects do not lead necessarily to better results. It depends on the type of mode locking techniques used. The highest and narrowest output pulses are obtained for specific values of the non linear parameters and the mean dispersion of the cavity.

In this paper, we design a WDM-RoF-PON based on multi-wavelength fiber laser and CSRZ-DPSK, which can achieve wire-line and wireless access synchronously without any RF source in ONU. The multi-wavelength fiber laser is the union light source of WDM-PON. By the RSOA and downstream light source reusing, the ONU can also omit laser source and makes the WDM-PON to be colorless. The networking has the credible transmission property, including wireless access and fiber transmission. The networking also has excellent covering range.

This paper is proposing an efficient traffic scheduling for routing in optical networks supported by Wavelength Division Multiplexing (WDM). Normally the traffic is routed through the primary path or back-up path towards the destination. In order to meet the transmission of higher data rates, the path of the WDM should be capable of carrying the traffic without any failure. Whenever the transmission through primary or backup path fails due to excessive overhead or network failure or congestion or excessive load, existing router mechanisms are not scheduling the traffic in an effective manner. This paper deals with an efficient traffic scheduling algorithm which effectively routes the traffic using multipath technique that satisfies the optical constraints. The whole procedure of routing algorithm is separated into two phases: the connection node establishment phase and multipath transmission from the connection node to destination phase. The connection node is selected on the basis of load and current traffic carrying capacity of that node. Then the traffic is routed to the destination using multiple paths. The proposed method tries to minimize the blocking probability of 70% compared to the existing Resource Efficiency Factor (REF) algorithm and also increase the throughput of 30% and better channel utilization of 23% based on data rate and 20% based on traffic time interval. Hence, the proposed algorithm is effectively routes the traffic within the network.

Optical code division multiple access (OCDMA) technique is required to meet the increased demand for high speed, large capacity communications in optical networks. In this paper, the transmission performance of a spectral amplitude coding (SAC)-OCDMA network is investigated when a conventional single-mode fiber (SMF) is used as the transmission link using 8DPSK modulation. The DW has a fixed weight of two. Simulation results reveal that the transmission distance is limited mainly by the fiber dispersion when high coding chip rate is used. For a two-user SAC-OCDMA network operating with 2 Gbit/s data rate and two wavelengths for each user, the maximum allowable transmission distance is about 15 km.

In traditional fast frequency-hopping OCDMA (FFH-OCDMA) system, beat noise and multiple-access interference are the main performance limitations, and complicated power control must be employed to eliminate the near-far effect. In this paper, a novel scheme of FFH-OCDMA with no-hit-zone sequence is proposed, which is named NHZ FFH-OCDMA. In NHZ FFH-OCDMA, the synchronization among users can be controlled within permissible time delay, and the code cross-correlation for different users equals zero. Therefore, near-far effect can be eliminated. Furthermore, beat noise and multiple-access interference also can be removed. Simulation of eight simultaneous users with dada rate 100 Mbit/s is demonstrated, where the fiber link consists of 50 km single-mode fiber, plus 5 km dispersion compensating fiber. Simulation results show that the near-far problem of NHZ FFH-OCDMA can be eliminated, and complicated power control can be removed. Therefore, this scheme is a good candidate for optical access network.

In this paper we analyze analog CATV transmission system where only one wavelength is used for transmission on which multiple analog RF channels modulated. We analyze different modulation distortions such as composite second order (CSO), composite triple beat (CTB) and intermodulation distortions at different frequencies. Good performance of CSO > −36 dBc and CTB > −41 dBc are obtained at 62.5 MHz, 125 MHz and 187.5 MHz in three tone directly modulated CATV transmission system.

This paper analyses the spectral efficiency of Optical Code Division Multiple Access (OCDMA) system using Importance Sampling (IS) technique. We consider three configurations of OCDMA system namely Direct Sequence (DS), Spectral Amplitude Coding (SAC) and Fast Frequency Hopping (FFH) that exploits the Fiber Bragg Gratings (FBG) based encoder/decoder. We evaluate the spectral efficiency of the considered system by taking into consideration the effect of different families of unipolar codes for both coherent and incoherent sources. The results show that the spectral efficiency of OCDMA system with coherent source is higher than the incoherent case. We demonstrate also that DS-OCDMA outperforms both others in terms of spectral efficiency in all conditions.

The full service access network (FSAN) task group meeting was held in April 2012, where they agreed to adopt time and wavelength division multiplexed passive optical network (TWDM-PON) as a primary solution to NG-PON2. Major requirements includes at least 40 Gbit/s aggregate rate in downstream, 1:64 split ratio, 40 km differential reach, and at least 1 Gb/s access rate per optical network unit (ONU). In this paper, a performance analysis will be carried out for downstream 4-wavelengths group selection from S-band, L-band, and C-band. A comparison for optimal transmitter design is also investigated among probable options of chirp managed laser diode, Lithium Niobate (LiNbo3) Mach Zehnder modulator, besides examining tunable transceivers in contrary to remotely fed colorless ONUs.

In this paper, we approximate the fundamental mode of guided propagation by involving an extension of the previous version of Improved Lorentzian parameter for single mode step index liner and nonlinear optical fiber within the scalar variational framework. We show this version gives better performance in terms of field, propagation constants group delay and waveguide dispersion on wider scale of V-values in comparison to earlier ones and works better in low-V region.

The Free Space Optical (FSO) communication system provides a high bandwidth, small size, light weight, low power and low cost alternative to present microwave systems. In this paper, we have designed a model of FSO system using OPTISYSTEM™ simulator to establish an FSO link by a range of 5 km with BER ∼ 10 −6 achieved and reported analysis of different parameter that play important role in FSO communication system.

A new two-dimensional OOC (optical orthogonal codes) named PC/MOCS is constructed, using PC (prime code) for time spreading and MOCS (modified one-coincidence sequence) for wavelength hopping. Compared with PC/PC, the number of wavelengths for PC/MOCS is not limited to a prime number. Compared with PC/OCS, the length of MOCS need not be expanded to the same length of PC. PC/MOCS can be constructed flexibly, and also can use available wavelengths effectively. Theoretical analysis shows that PC/MOCS can reduce the bit error rate (BER) of OCDMA system, and can support more users than PC/PC and PC/OCS.

This paper presents the practical analysis of the optical code-division multiple-access (O-CDMA) systems based on perfect difference codes. The work carried out use SNR criterion to select the optimal value of avalanche photodiodes (APD) gain and shows how the mismatch in the splitters and gains of the APD used in the transmitters and receivers of network can degrade the BER performance of the system. The investigations also reveal that higher APD gains are not suitable for such systems even at higher powers. The system performance, with consideration of shot noise, thermal noise, bulk and surface leakage currents is also investigated.