H.K. Dixit

Optical computing with semiconductor optical amplifiers

Increasing communication traffic and plans to increase various services may cause a serious problem towards the power consumption of network equipment. One of the causes of large power consumption in the present network is the multiplexing scheme, such as wavelength division multiplexing (WDM) and electrical routing of the packet signals. WDM requires O/E (optical to electrical) and E/O (electrical to optical) signal con- version circuits with the same number as that of wavelength, resulting in an increase in power consumption. In addition to this electrical signal pro- cessing for the IP packet, routing, and switching at the router consumes a large amount of power. If we could process ultrafast signals using electro- magnetic light waves without converting to electrical signals, this would reduce the power consumption of routers. One of the ways to overcome these problems is the development of all-optical computing devices. All-optical computing devices are based on the nonlinear interaction of light waves, which is an electromagnetic wave. The use of electromagnetic light waves makes computing, such as switching, possible at very high frequencies of more than 100 GHz. We discuss all-optical computing devices based on semiconductor optical amplifiers with the main emphasis on all-optical logic gates.

Performance study in dispersion compensation techniques with Duobinary format at different bit rates

In this work comparative study is carried for high speed duo binary transmitter with different dispersion compensation schemes for long haul optical communication. These techniques are applied to duo binary system, which operates at bit rates of 10, 15 and 20, 25,30Gbps bit rates. The dispersion compensation schemes tested are Pre-compensation & Post-compensation, symmetrical configuration1&symmetrical configuration 2, optical phase conjugation, FBG compensation, double hybrid fiber& dispersion fiber managed for long haul optical communication. Eye opening is better at 10Gbps bit rate optical transmission with all dispersion compensation techniques tested. It is found that for higher bit rates dispersion managed fiber and next one FBG compensation shows better performance metrics like eye opening bit error rate and factor Q as compared to other dispersion compensation schemes. It is also observed that for low input laser power transmission performance metrics are much better for all dispersion schemes and at higher laser input power transmission performance metrics are degraded.

Ultrafast all-optical 4-bit digital encoders using differential phase modulation in semiconductor optical amplifier-Mach-Zehnder interferometer configuration

Abstract. A novel approach for all-optical digital encoder for both binary-to-gray code and gray-to-binary code have been proposed. Design is based on the basic concept of digital encoder using the exclusive OR (XOR) addition. The XOR gate used in these encoders has been implemented using differential phase modulation between two arms of the Mach-Zehnder interferometer (MZI), in which a semiconductor optical amplifier is placed symmetrically in both arms of MZI. For the most severely degraded output bit, i.e., least significant bit for gray-to-binary encoder, the extinction ratio obtained is 2.35 while the minimum bit error rate is zero at 10  GB/s. For the second most significant bit of gray-to-binary encoder and for all the three bits except the most significant bit of binary-to-gray encoder, the extinction ratio obtained is around 27 dB. For the most significant bit, as input and output bits are same, the extinction ratio is very high, approaching infinity.

Study in order and width of RZ super Gaussian pulse for different bit rate optical communication link with dispersion managed SMF (G655)

In this paper performance study for optical transmission link with Super-Gaussian pulse of different order, pulse width with different optical filters, full width at half maximum (FWHM) and bit rates 10, 15, 20,25Gbps has been tested. The performance is compared for 6dBm value of Er-doped fiber amplifier (EDFA) power for optimum performance. The graphical result shows dependency of pulse width and order of RZ super-Gaussian optical pulse on optical transmission performance. It shows that to decrease BER and timing jitter in the system, smaller width and 3rd to 5th order super Gaussian pulse, full width at half maximum (FWHM) 10ps to 60ps should be used. It is observed that raised cosine filter better performance among the various optical filters.

Investigation of XOR operation in all-optical system with NRZ, RZ and Manchester modulation formats

The paper investigates the suitability of various data formats for optical XOR gate at 10 Gb/s. The investigation is focused on different data formats for high-speed optical networks in optical XOR gate. The extinction ratio at different bit rate is compared based on suitability of various data formats. If the clock is pulsed and modulation is RZ or Manchester then good results observed for extinction ratio as compared to NRZ.

Study in F.O.C. Multiplexing Techniques-A Review

Study in F.O.C. Multiplexing Techniques-A Review Communication network bandwidth requirement is growing at stunning rate, consequently numerous multiplexing techniques have been proposed by contributors for the augment in spectral efficiency from time to time. In this view the paper presents profound review on numerous multiplexing techniques for fiber optic communication, such as wavelength division multiplexing, optical time division multiplexing, optical code division multiplexing, optical orthogonal division multiplexing, mode division multiplexing, space division multiplexing, polarization division multiplexing and duty cycle division multiplexing technique.

Arc-path working capacity allocation planning in survivable WDM optical networks

Survivability is an ability of a network to withstand and recover from failures; it is one of the most important requirements of the network. Survivability requires resources for handling the failures. So, efficient resource allocation strategy is required for survivability. This manuscript presents simple integer linear program (ILP) formulations for arc-path working capacity allocation model. This model provides 100% secure protection against link failure. The capacity utilization for network A (six-node), network B (eight-node) & National Science Foundation Network (NSFNET) has been thoroughly analyzed.

Performance Study of Novel Designed Hybrid WDM System

Performance Study of Novel Designed Hybrid WDM System This article presents investigation of the proposed hybrid WDM scheme with mixed data rates (10 and 20 Gbps), different modulation schemes and unequal channel spacing (100 GHz/50GHz). The investigated hybrid system consists of five transmitters and each transmitter has four channels having total capacity of twenty channels. Numerous optical modulators such as linear modulator, DPSK modulator, Sin2 modulator, Dual Arm Balanced and unbalanced MZM have been implemented on the transmission links. The simulated results depicted excellent performance with linear modulator, phase modulator while unbalanced MZM has showed degraded transmission performance for arbitrarily selected transmission distances 200 km, 320 km and 360 km. Hence, the study of hybrid WDM system illustrates that it can be capable scheme for further augment in spectral efficiency and significant viable option for the present and future active, passive optical networks.

Design of all-optical NOT gate using SOA based Mach-Zehnder interferometer at 1.0Gb/s

The paper presents, the simulation of optical Boolean NOT gate with SOA based Mach Zehnder Interferometer. Wavelength converter is a key element for the design. Wavelength converter translate optical signal of one wavelength into optical signal of another wavelength. In the design of NOT gate the combination of control and continuous clock pulse are properly selected so that SOA is heavily saturated and at the same time the switched out continuous clock pulse are compressed by the control pulse. However, the operation is limited by SOAs recovery time.

Optimization of 2x2 Mach-Zehnder Interferometer Electro-Optic Switch

This paper presents enhanced performance of a 2x2 optoelectronic switch based on Mach-Zehnder Interferometer made by titanium diffusion in lithium niobate substrate. The electro-optic switches have wide application in next generation optical networks due to their high speed operation. The optimization of switching characteristics is performed for low switching losses such as insertion loss, excess loss, high extinction ratio and low switching voltage by varying the gap of 3dB couplers, gap of interferometric arms and wave guide width. The present structure has been optimized in order to reduce the overall switch losses (= 0.1 dB) and to achieve the best possible extinction ratio (≥ 20 dB). Further by changing wave guide width the switching voltage is reduced from 7.8 V to 7.4 V.