Nar Singh

Nonlinear Effects in Optical Fibers: Origin, Management and Applications

The nonlinear effects in optical fiber occur either due to intensity dependence of refractive index of the medium or due to inelastic-scattering phenomenon. This paper describes various types of nonlinear effects based on first effect such as self-phase modulation, cross-phase modulation and four-wave mixing. Their thresholds, managements and applications are also discussed; and comparative study of these effects is presented.

SOLITON BASED OPTICAL COMMUNICATION

The group velocity dispersion (GVD) imposes severe limit on information carrying capacity of optical communication systems. By choosing appropriate pulse shape highly stable light pulses known as solitons are generated when effect of GVD is balanced by self-phase modulation (SPM). The application of solitons in communication systems opens the way to ultrahigh-speed information superhighways. Transmission speed of order of Tbit/s can be achieved if optical amplifiers are combined with WDM in soliton based communication systems.

Nonlinear Scattering Effects in Optical Fibers

The nonlinear scattering effects in optical fiber occur due to inelastic-scattering of a photon to a lower energy photon. This paper describes stimulated Brillouin scattering and stimulated Raman scattering processes. Their thresholds, reduction in power penalty and applications along with comparative study of these effects are also presented.

REDUCTION OF CROSSTALK IN WAVELENGTH DIVISION MULTIPLEXED FIBER OPTIC COMMUNICATION SYSTEMS

In this paper two new methods to reduce the crosstalk in WDM systems are presented. These two methods along with the present methods are analyzed and their performances are compared. The proposed methods yield better results. Both signal power and optical signal power to noise power ratio (OSNR) improve significantly.

L-band Superfluorescent Fiber Source

An L band superfluorescent fiber source (SFS) is presented. The spectrum covers wavelengths from 1560 nm to 1615 nm. The L band SFS is constructed by a low power L band amplified spontaneous emission (L-ASE) seed source and a high power erbium-ytterbium co-doped fiber (EYDF) amplifier in double pass configuration. The output power of 0.72 W is obtained under 5.0 W, 980 nm pump power.

S-band distributed raman fiber amplifier

This paper presents the gain and noise figure optimization of Raman fiber amplifier in S-band for single-mode fiber (SMF) and dispersion-shifted fiber (DSF) by using WDM pumping scheme. For single-mode fiber 16 dB gain with 50 nm bandwidth and for dispersion-shifted fiber 19 dB gain with 40 nm bandwidth is obtained. In both cases noise figure is also achieved.

Optimization of standards for video compression tools over wireless networks

In recent past mobile communication has grown rapidly. With the exponential growth, the need for the robust transmission of multimedia information, audio, video, text, graphics, and speech data-over wireless links are becoming an increasingly important application requirement. Since the video data may occupy more bandwidth than the other media data during transmission, it should be given more emphasis in the wireless multimedia communication. A number of International standards have been established based on different application technology and era. MPEG-4 standard has much broader perspective to support high and low bitrate multimedia application but the new video compression standard H.264/AVC or MPEG-4 part-10 promises better rate distortion performance and compression efficiency. This paper aims to present fully optimized H.264/AVC encoder to show its suitability among the different standards for mobile and other application of wireless networks. Various encoding and decoding implementation techniques to optimize H.264/AVC video encoder at low bit-rate has been discussed.

Performance of 40 Gbps RZ Single-Channel Transmission Over Hybrid Fibers

The performance of 40 Gb/s RZ single-channel transmission over 500 km using single mode fiber (SMF) with dispersion compensating fiber (DCF) and reverse dispersion compensating fiber (RDF) is evaluated. For moderate input power level SMF + RDF system works well, while SMF + DCF system performs better for input power level greater than 10 dBm. The performance is evaluated by using Q-factor and optical eye-diagram.

Design and performance analysis of dispersion managed system with RZ and NRZ modulation format

In this paper, DWDM system with post dispersion compensation is investigated using different modulation formats. HOA (Raman-EDFA) used to increase the power transmission wavelength in optical network. The result obtained on increasing the input power for different modulation format are compared with the help of parameters like bit error rate, quality factor and extinction ratio. It was observed that NRZ (non-return to zero) format BER is less than 10−72 and extinction ratio is 9.7dB whereas RZ (return to zero) format bit error rate is as low as zero and high extinction ratio of 13.57dB. Analysis the above performance parameters it can be easily concluded that RZ format is much better than NRZ format for post dispersion management.

Soliton based Optical Fiber Communication: At a Glance

The paper presents a latest review on “soliton based optical fiber communication systems”. It gives a brief description about Group-velocity dispersion (GVO) and Self- phase modulation (SPM), both of which play the main role in the formation of soliton pulses. It also describes the combined effects of GVD & SPM, modulation instability, solitons properties, transmitters and attenuation management techniques.