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All optical wavelength converter (AOWC) play important functionalities to enhance the network reconfiguration, efficient wavelength routing and assignment, non-blocking capacity in future dynamic optical access networks. In optical access networks, bandwidth limitation and wavelength continuity constraints lead to inefficient utilization of wavelength resources. AOWCs are the premier option to cope with these network constraints. On the other hand, advanced modulation formats have been extensively analyzed and used to achieve the high spectral efficiency. Since advanced modulation formats are more sensitive to amplitude and phase noise, AOWC are more suitable to achieve minimum power penalty and maximum conversion efficiency. In this paper, AOWC based on four wave mixing (FWM) in highly nonlinear fiber (HNLF) for coherent 100 Gbps dual-polarized differential quadrature phase shift keying (DP-DQPSK) has been designed. The performance of AOWC is optimized at different probe input power, different pump power and wavelength to achieve the maximum conversion efficiency. After the multiwavelength conversion based on 0.7 km HNLF, the power penalty for converted 100 Gbps DP-DQPSK signals is less than 4.15 dB at BER of 10-9 and maximum conversion efficiency of −10.58 dB has been achieved.

In this work, we proposed a simple mathematical model to explain the formation of grating structure in photosensitive germane-silica fibers written by KrF excimer laser and phasemask. In the observation, the growth of local index changes in the fiber in the bright fringes and dark fringes of the interference field share similar characteristics and can be represented by a single characteristic function. Through curve-matching technique, the interference visibility and the evolution of grating visibility during grating inscription can be determined.

In this paper, a 340-Gb/s polarization shift keying-dual polarized-differential quadrature phase shift keying (PolSK-DP-DQPSK) orthogonal modulation for next generation high-capacity optical transmission systems has been proposed. The NRZ-PolSK and DP-DQPSK are considered to investigate the performance for higher order optical modulation in 50 GHz spaced wavelength division multiplexing (WDM) optical network. In the system architecture, eight 340-Gb/s PolSK-DP-DQPSK orthogonal modulated WDM channels have been transmitted over 1000 km of SMF + DCF. The influence of different network parameters such as input power, channel spacing, transmission distance etc. are considered to analyze the performance of orthogonal modulated signals in WDM optical network. This new modulation scheme has high spectral efficiency and very low phase noise in WDM optical network. The WDM system achieved the spectral efficiency of 6.8b/s/Hz for the 400 GHz bandwidth. Further, increase in the spectral efficiency represents the most attractive approach in the transport capacity of future long-haul optical transmission systems.

Duty Cycle Division Multiplexing (DCDM) hasbeen shown to be able to improve utilization of the optical bandwidth. However, the challenge arises on its signal recoveryat the receiver ends. Decision making protocol plays an important role to determine the correctness of its regenerated data. Previous approach regenerate inaccurate data due to its assumption that all received signals are valid. Thus, the automatic mapping is used in their decision process with no consideration on invalid signals. Due to this motivation, we design a new signal recovery protocol for DCDM. In this protocol, the signal properties such as amplitude level, distance between slots, number of slot change and probabilities of occurrence are used in order to discriminate the received signal into an appropriate data. The simulation is established through OptiSystem simulator and Matlab programming. It is observed that an improvement of the BER by 16.2 percent can be achieved using the new proposed protocol.

A new multiplexing technique based on duty cycle division is proposed, thus the name duty cycle division multiplexing (DCDM). DCDM can be applied in both electrical and optical domains, for wired and wireless systems. The new technique allows for more efficient use of time slots as well as the spectrum, taking advantage of both the conventional TDM and FDM. In this paper, three channels operating at the same speed of 10 Gbps per channel are multiplexed in the electrical domain. The performance comparison is made against 3times10 Gbps TDM, and the experimental simulation results show that the DCDM system can support higher bit rate than TDM and also, it is less sensitive to the chromatic dispersion effect.

In this paper, duty cycle division multiplexing (DCDM) is proposed as an alternative multiplexing technique. It can be applied in any communication systems, although the focus in this paper is in optical fiber communications. In this paper, we examine 3 channels each operating at 10 Gbps modulation rate over a single optical carrier. The performance comparison is made against 30 Gbps RZ transmitted pulses, time domain multiplexed (TDM). The results show that at a fixed transmission power, DCDM can support longer distance than that with RZ TDM technique. Also, the results show that RZ-TDM pulses require 35.5 dB more SNR to support the same distance as that for DCDM.

A new multiplexing technique based on duty cycle division is proposed, under the name: absolute polar duty cycle division multiplexing (APDCDM). The new technique allows for more efficient use of time slots as well as the spectrum, taking the advantage of both the conventional TDM and FDM. The basic properties based on theoretical analysis as well as simulation studies have been done to evaluate the performance of this technique based on the signal energy and symbol error rate (SER). In this paper the performance of absolute polar duty cycle division multiplexing is compared with multilevel M-ary as well as with the time division multiplexing (TDM) techniques. The simulation has been set for wireless transmission based on free space propagation model with adaptive white Gaussian noise (AWGN). PSK and QAM are used as modulation schemes to evaluate these techniques against data rates and number of users. The study shows that by increasing the number of users, the energy per bit in APDCDM has better performance than that of TDM technique. The simulation result correspond with the theoretical study shows that absolute polar duty cycle division multiplexing (APDCDM), has better SER than TDM.

A duty cycle division multiplexing (DCDM) is proposed as an alternative multiplexing technique. It can be applied in either wired or wireless communication systems, although the focus in this paper is in optical fiber communications. The channel multiplexing and demultiplexing is performed electrically at single user bit rate which is very economic. In this paper, we examine 3 channels each operating at 10 Gb/s over a single optical carrier. The performance comparison is made against return-to-zero (RZ) transmitted pulses. Back-to-back receiver sensitivity and required optical signal-to-noise ratio (OSNR) of this system are examined and compared with 10 Gb/s RZ pulses. Effect of the chromatic dispersion is tested for DCDM channels and compared with 30 Gb/s RZ coding at the same transmission power. Also, the launched power of these two techniques is measured against system dispersion at BER of 10-9. The results show that, DCDM can support higher amount of chromatic dispersion than that RZ technique. In the end, receiver sensitivity and OSNR of 3-channel DCDM is tested at different bit rate of 2.5, 10, 25 and 40 Gb/s. A receiver sensitivity and OSNR of -16.8 dBm and 34.6 dB is required for the worst DCDM user when the system running at 3 times 40 Gb/s respectively.