Volume 41, Issue 1 -

We present a model of a Raman-parametric hybrid amplifier for flat gain amplification of narrowband Dense Wavelength Division Multiplexed (DWDM) terabits capacity system. In the proposed configuration Raman pump has been cascaded with one – pump parametric amplifier. While Raman amplifier typically uses a long length single mode fiber as a gain medium, the Fiber Optical Parametric Amplifiers (FOPA) uses a small length of Highly Non-Linear Fibers (HNLF). This allows for maximum optimization of the gain achieved using Raman as well as parametric processes. We focus on the signal degradation due to non-linear crosstalk arising because of multi-pump configuration, in particular, due to the generated idlers within the operational bandwidth. As the channel spacing is reduced, fiber non-linearities increase significantly. The dilemma to use the fewer number of high powered pumps Vs, the use of increased number of relatively low powered pumps has been investigated for DWDM system. The optimization of the pump powers has been evaluated in terms of signal degradation, gain, gain variation and OSNR. It has been demonstrated that a maximum gain of 45.38 dB for 96×40 Gbps, 25 GHz system is attainable up to 200 km of transmission distance while maintaining OSNR>18 dB using the proposed hybrid. No gain compensation or gain optimization technique has been used. The findings of this work establish flat gain in narrowband DWDM systems is achievable through proper optimization of pump wavelengths and their powers.

Free space optics (FSO) is well-competent and premier technology to cater the high speed services in different geographical areas such as hilly areas and inter building network. In this paper, we successfully demonstrated the spectrum sliced wavelength division multiplexed FSO system. In order to make system bandwidth efficient, frequency spacing of 75 GHz is taken among the wavelength division multiplexing ( WDM) channels. Carrier spectrum broadening is achieved for spectrum slicing through the nonlinearity called self-phase modulation. Moreover, requirement of multiple laser sources is eliminated. However, in conventional WDM systems, n numbers of lasers are needed to generate n WDM channels. To strengthen the signal in this FSO system, three optical amplifiers are scrutinized such as erbium-doped fiber amplifier (EDFA), semiconductor optical amplifier (SOA) and Raman amplifier in terms of Q-factor and bit error rate (BER). Results revealed that EDFA is best amplifier in proposed SS-WDM-FSO system.

Optical networks were invented by the developing and developed nations in order to extend the capacity required for communication systems in a worthwhile way. In this paper, the attempt is done to improve the capacity and performance of semiconductor optical amplifier, Raman and erbium-doped fiber amplifier (EDFA) amplifiers used in optical networks. The potential of different optical amplifiers operating at 8×10 Gbps has been examined and their performance was compared on behalf of different parameters, viz. eye opening, eye closure, jitter, quality factor and transmission distances. It was observed that EDFA provided the consistent good quality of communication for long-distance transmission up to 150 km along with better eye opening and eye closure with acceptable jitter performance. Further, it is observed on the basis of quality factor and bit error rate that EDFA gives comparably better performance than Raman amplifier. Moreover, it is seen that as the data rate of the system increases, the quality of communication signals starts decreasing.

In this paper, we have simulated an optical 32 channel WDM system with 10 Gbps data rate for various hybrid amplifiers at varying lengths. Stand-alone EDFA gives better performance than other individual amplifiers but when hybrid with Raman amplifier, the performance of the WDM system is enhanced. A lot of researchers are working on the hybrid amplifiers like EDFA and Raman. In this research paper we have also included latest amplifier such as Ytterbium and Praseodymium amplifiers and the performance of the various hybrid combinations is compared. So, different hybrid amplifiers such as Raman-EDFA, EDFA-Yb, Raman-Yb, EDFA-Pr and Raman-Pr have been analyzed for performance parameters like quality factor, bit error rate, eye height and channel power. The analysis shows that EDFA-Pr has maximum Q-factor of 15.4883 at 80 km. EDFA-Pr has a maximum eye opening of 0.00534 at 80 km of length but at 120 km transmission distance EDFA-Yb shows maximum eye opening of 0.00154. Below 100 km of transmission distance, EDFA-Pr shows minimum BER value ranging from 10 –54 to 10 –20 but as the length is increased above 100 km EDFA-Yb shows better performance with values ranging from 10 –16 to 10 –09 .

In recent years, free space optical communication (FSO) has become a leader for its unique characteristics: large bandwidth, unlicensed spectrum, simple implementation, low power and high data rate. However, we use as a transmission medium for Spectral Amplitude Coding-Optical Code Division Multiple Access SAC OCDMA system. In this paper, we investigate the optimum received power of FSO communication system employing SAC OCDMA, by using different detection technique, such us Spectral Direct Detection SDD and Single Photodiode Detection (SPD) technique under optical Gaussian filter decoder schemes with Modified Double Weight code (MDW). In this work, the adverse effects of atmospheric channel limit the possibility of a large FSO communication, moderate turbulence and hazy weather conditions are considered. The results show that the performance of the proposed system with wavelength-division-multiplexing (WDM) multiplexer (MUX) based on Gaussian optical filter with SDP detection fares better than the system employing SDD technique.

We have proposed simple ring resonator 5-channel demultiplexer based on optical channel drop filter analysis that is applicable at third communication window (1550 nm) range. Our proposed base filter is the important part in designing the demultiplexer, inclusive one ring resonator contains one square dielectric rod at core. Demultiplexer structure introduced by arranging five filter with different ring core refractive index. Insomuch every ring core have individual refractive index, thus each ring have diverse resonant wavelength. Numerical results by the finite difference time domain (FDTD) method show quality factor (Q) and transmission efficiency of fundamental channel drop filter are 1038 and 93 %, respectively. It is found that transmission efficiency in designed demultiplexer is more than 90 % for each channel; channel spacing is less than 4.2 nm. The average crosstalk value, total footprint of demutiplexer is −17.85 dB, 689.61 μm 2 , respectively. Small size with a very simple ring design can be benefit in photonic integrated circuit.

The performance of localized surface plasmon resonance-based sensor with and without Bragg grating by using finite difference time domain method is evaluated with nanoparticles used at the tip of optical fiber. The proposed sensor has been analyzed in terms of refractive index (RI) sensitivity and signal-to-noise ratio (SNR). It is observed that the RI sensitivity of surface plasmon resonance sensor is 240 nm/RIU with and without grating as RI of surrounding varies from 1.4 to 1.5. It is found that the value of SNR is 0.875 RIU →1 without grating and 2.75 RIU →1 with grating. So there is an improvement in the SNR when the Bragg grating is inscribed within the core of the fiber.

The photonic crystals (PhC) play an important role in building all optical logic devices and also recommended as solution for opto-electronic bottleneck in terms of speed and size. This paper put forward a design of XOR gate using Photonic Crystal Ring Resonator (PCRR). The ring resonator is a device which provides output on the basis of coupling of mode fields from a linear waveguide to circular ring. The proposed work is designed using two-dimensional (2D) square lattice photonic crystals within the dimensions of 37a×37a$\left( {37a \times 37a} \right)$ by putting silicon (Si) rods in silica (SiO 2 ). The study of device is carried out using finite-difference-time-domain (FDTD) method and verified using MATLAB.

In this study, a simulation analysis of 40-Gb/s long-haul (120 km) dense wavelength-division multiplexer system (DWDM) of 32 channels with 50 GHz spacing is conducted for duobinary return-to-zero modulation formats. Pre- and post-dispersion compensation schemes utilizing dispersion compensating fiber (DCF) and fiber Bragg grating (FBG) are analyzed to compare these schemes at high bit rate. Quality factor (Q) and bit error rate (BER) values are used to measure the response of the system as a function of input power for both compensation schemes. The pre-FBG scheme shows a better performance in terms of Q-factor that reached 11.5 at 0 dBm input signal power.

The power series formulation for modal field of single-mode graded index fibers by Chebyshev technique has worked excellently in predicting accurately different propagation characteristics in simple fashion. Here we develop a simple iterative method involving Chebyshev formalism to predict the modal field of single-mode graded index fiber in the presence of Kerr-type nonlinearity. Taking step and parabolic index fibers as typical examples, we show that our results match excellently with the available exact results obtained vigorously. Thus, the reported technique can be considered as an accurate alternative to the existing cumbersome techniques. Accordingly, this formalism will be beneficial to the technologies for evaluation of modal noise in single-mode Kerr-type nonlinear graded index fibers.

To fully utilize the existing optical network resource, the dynamic traffic grooming technology, which could efficiently multiplex many low-speed services arriving dynamically onto high-capacity optical channels, has been studied extensively and used widely. In this article, the problem of dynamic traffic grooming in joint optimization of IP over elastic optical network (EON) is studied. This problem consists of three sub-problems at two layers: the routing problem at the IP-layer (IPR), the routing, modulation level (RML), and the spectrum allocation (SA) problems at the optical layers. We proposed a novel topology-integration and adaptive-modulation based in cross-layer routing spectrum allocation (CL-RSA) algorithm, which follows a multi-cost approach that solves the IPR, the RML, and the SA problems jointly. The most important features of the proposed algorithm are merging physical topology with virtual topology and using the minimum-weight preferred method for route selection. Meanwhile, the effect of physical-layer impairments (PLI) on signal transmission is considered. In addition, the adaptive modulation scheme is used to allocate the spectrum resource. The simulation results show that the algorithm can effectively improve the spectrum resource utilization and reduce the network blocking probability compared to other algorithms in various network conditions, especially in the high load condition effectively.

As the optical networks are moving towards transparent networks, the Optical-to-Electrical (O-E) conversion taking place within the link is reduced to minimal. This results into accumulation of physical layer impairments along the light path, thereby degrading the signal quality. Due to enormous data traffic carried by optical links, any link failure or non-recovery to data at the destination end may result in huge loss. To improve the system performance, the optimum placement of regenerators is one of the solutions for the same, where signal regeneration may takes place at certain pre-specified nodes. Three different strategies of regenerator placement are discussed in the present work. The improvement in system performance with this is also presented.

In this paper, we examine the hybrid optical fiber (OF)/free-space optics (FSO) architecture for a backhaul downlink over a wavelength-division multiplexing passive optical network (WDM-PON). The hybrid backhaul architecture is able to provide not only high-data-rate but also flexibility and quick deployment. The performance analysis is carried out for the hybrid OF/FSO backhaul downlink over a four-wavelength WDM-PON under the effect of four-wave mixing (FWM). The impact of atmospheric turbulence-induced fading and major noise components, including amplifier’s noise, shot noise, beat noise, background noise, and thermal noise, is also taken into account. The numerical results show that, although high transmitted power and amplifier’s gain at the transmitter side help to mitigate the impact of noise and fading, they should be limited to a specific value to avoid the influence of FWM. Therefore, the use of amplifier or avalanche photodiode at the receiver side would be a better solution to keep the bit-error rate (BER) at the low levels.

Radio overfree space optics (Ro-FSO) is a modern communication technique that promises a development future. In this paper, WDM Ro-FSO communication system has designed (10 Gbps×8λ) for transmissions 80 Gbps data rate via the largest possible distance under clear air, heavy rain, and heavy fog atmosphere conditions of FSO link, with test the best wavelengths performance of (193.1 to 93.8) THz that each one (wavelength) carry 10 Gbps by employ BER analyzer at receiver channels. The electric signals produced by phase shift keying (PSK) modulation technique modulated the information (10 Gbps) on RF signal (20 GHz). The results of transporting 80 Gbps were 5 km under clear air weather condition, 1.2 km under heavy rain, and 0.2 km under heavy fog condition. Finally, the different wavelengths that carry high-value data rate are tested by measurement of the BER and Q factor for each received channel, and the theoretical model of PSK modulation is analyzed.

In this article we designed an optical filter based on 1D photonic crystals. Then optimized the proposed structure using genetic algorithm. The proposed filter was designed using generalized Thue–Morse series. After optimizing the proposed structure, we can improve the quality factor of the proposed structure.