Amin Malekmohammadi

Duty-Cycle Division Multiplexing: Alternative for High Speed Optical Networks

Performance of 3×10 Gbps duty-cycle division multiplexing (DCDM) is analyzed. The channel demultiplexing is performed electronically at single user bit rate (10 Gbps). At 30 Gbps, null-to-null spectral width of 80 GHz is measured for DCDM technique which is 33.3% less compared to 30 Gbps conventional return-to-zero (RZ). In this system, the worst channel required a receiver sensitivity of around -25.6 dBm at bit error rate (BER) 10-9. The chromatic dispersion tolerances of the system are 210.5 and 236 ps/nm for the worst and the best channel respectively.

A new multi-slot and multi-level coding technique for high capacity communication system

A new multi-slot and multi-level coding technique for high capacity communication system, known as Multi Slot Amplitude Coding (MSAC) is presented. This technique offers better flexibility in terms of defining the symbol based on time slot and signal level in order to generate more unique symbols as a line code with better clock information since all the symbols have zero level (return-to-zero) at the beginning. A set of mathematical equations have been established to relate the parameters of MSAC symbol properties. Theoretical analysis to evaluate the performance of this technique based on the number of slot and the number of signal level against conventional Time Division Multiplexing (TDM), multilevel Mary signaling, and Duty Cycle Division Multiplexing (DCDM) are discussed. The comparison shows that MSAC technique is capable to maximize the number of supportable tributaries with better utilization of the slot and the signal level.

Power Efficiency Evaluation of Mapping Multiplexing Technique and Pulse Amplitude Modulation for Noncoherent Systems

The two-, three-, and four-channel mapping multiplexing technique (MMT) is demonstrated to increase the data capacity of multilevel intensity-modulated transmission formats to 2, 3, and 4 bits/symbol with a substantial reduction in power penalty. This paper outlines the N-channel MMT design metric consideration influence on the performance enhancement of higher order amplitude modulated systems in terms of power penalty, receiver sensitivity, and spectral efficiency. The signal space model has been developed for N-channel MMT, where the average electrical and optical power expressions are derived. Transmission of 2, 3, and 4 bits/symbol using MMT system shows better performance in terms of the average optical power penalty, in comparison with pulse amplitude modulation (M-PAM) formats, with respect to the information capacity. The proposed scheme can be considered as an alternative to M-PAM systems with enhanced power efficiency.

Absolute Polar Duty Cycle Division Multiplexing (APDCDM); Technique for wireless communications

A new multiplexing and demultiplexing technique for wireless communications which is called Absolute Polar Duty Cycle Division Multiplexing (APDCDM) is presented in this paper. APDCDM can become an alternative multiplexing technique in wireless communications. The new technique allows for better error detection, correction, clock recovery and more efficient use of time slots as well as spectrum. The principle of the APDCDM technique has been discussed in this paper based on theoretical analysis as well as simulation studies. The performance comparison is made against time division multiplexing technique (TDM). The simulation has been set for wireless transmission, based on free space propagation model with adaptive white Gaussian noise (AWGN); QAM is used as modulation scheme to evaluate this technique against data rate and number of users. The simulation result correspond with the theoretical study show that APDCDM has better performance than TDM for supporting higher number of multiplexing users and bit rate.

Performance improvement of Mapping Multiplexing Technique (MMT) using Dual-Drive Mach-Zehnder Modulator at 40 Gb/s

A methodology to control the eye opening distribution of Mapping Multiplexing Technique (MMT) system is proposed and presented. We modeled and analyzed a method to enhance the receiver sensitivity of MMT system by using optimized Dual-Drive Mach-Zehnder Modulator (DD-MZM). The proposed method offers larger eye opening for distorted higher-level eyes. Based on the numerical calculation, the optimization leads towards minimal eye closure in comparison to conventional MMT system. In comparison to the conventional MMT system, the optimization leads in to the 6.1 dB improvement in terms of receiver sensitivity.

Experimental demonstration of Absolute Polar Duty Cycle Division Multiplexing

The authors report experimental demonstration of a 2-channel (2 × 2.5 Gb/s) Absolute Polar Duty Cycle Division Multiplexing (AP-DCDM) system, using a single modulator over a single wavelength. The back-to-back receiver sensitivities and chromatic dispersion tolerance (at BER=10−9) for the worst AP-DCDM channel were −41.7 dBm and ∼ + 365 ps/nm, respectively. It is demonstrated that 5 Gb/s (2 × 2.5 Gb/s) AP-DCDM has a spectral width of 10 GHz.

Proof-of-Concept Experiment of Duty Cycle Division Multiplexing with Bit Error Rate Analysis

Demultiplexing concept of Duty-Cycle Division Multiplexing (DCDM) technique is tested in the back-to-back connection and after transmission over copper wire and optical fiber. Three different lengths of copper wire are tested with the total loss of 3.3, 6.6, and 9.9 dB respectively. Even though the sampling points and threshold values were not dy- namic, the demultiplexing process for the case of back-to-back, and after transmission over the links with 3.3, and 6.6 dB losses, was successful without experiencing any errors. This can be witnessed when the recovered data is compared against the transmitted bits. However, the errors are recorded in the link with 9.9 dB losses, which was mainly due to the non-optimized sampling points and threshold values. In experiment over 60 km Standard Single Mode Fiber, successful transmission was demonstrated. The receiver sensitivity is calculated off-line by using bit error rate analysis. These results confirm the validity of DCDM demultiplexer structure including the sampling process and the data recovery rules.

An alternative to M-PAM transmission system featuring improved receiver sensitivity for optical interconnects

Two, three, and four-channel Mapping Multiplexing Technique (MMT) is demonstrated to increase the data capacity of multilevel intensity modulated transmission formats to 2, 3 and 4 bits per symbol with substantial reduction in power penalty.

A novel economical duty cycle division multiplexing with electrical multiplexer and demultiplexer for optical communication systems

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.

30Gb/s Absolute Polar Duty Cycle Division Multiplexing In Dispersion Uncompensated Optical Systems

In this study the author has modeled and characterizes the performance of 3times10 Gbp/s absolute polar duty cycle division (APDCDM) multiplexing in dispersive environments at 1550 nm. APDCDM technique is examined, with comparison to non-return-to-zero (NRZ) and return-to-zero (RZ) time division multiplexing. In this paper three channel operating at the same speed of 10 Gbps are multiplexed in electrical domain. The experimental simulation results show that the receiver sensitivity of all users in APDCDM system is similar to that of RZ-TDM and 3 dB better than NRZ-TDM. The proposed system offer reduced dispersion sensitivity; this suggests advantages for APDCDM in optical multiplexing systems. It was also showed that APDCDM can support higher bit rate than TDM and also, it is less sensitive to the chromatic dispersion effect.