Design and Analysis of Binary Driven Coherent M-ary Qam Transmitter for Next Generation Optical Networks

This work presents a design for a binary driven optical square M-ary quadrature amplitude modulation (QAM) transmitter for high speed optical networks. The transmitter applies tandem quadrature phase shift keying (QPSK) modulators to eliminate the need for linear broadband amplifiers and high-resolution digital to analog converters (DACs), which are both required by conventional transmitters. The transmitter design could be scaled to any order of square M-ary QAM by simply adding more QPSK modulators in tandem. It also provides a Gray coded symbol constellation, insuring the lowest bit error rate possible during symbol recovery. We also provide the design for the coupling ratios of the optical couplers that take into account the insertion loss of the optical components, in order to generate a proper 16-QAM and 64-QAM symbol constellation with equally-spaced symbols. Additionally, we analyze the impact of coupling ratio errors as well as phase errors on the bit error rate (BER) performance and constellation diagrams. The performance is tested using the OptiSystem simulation at 50 Gbaud and under presence of additive white Gaussian noise (AWGN), which demonstrated high quality symbol constellation and a BER performance similar to theoretical expectations. For 16-QAM, a BER better than 10-4 and power penalty of about 2 dB are achieved for coupling ratio errors less than 10 %, or phase errors within ±7 degrees. The 64-QAM transmitter, on the other hand, demonstrated a BER better than 10-4 and power penalty of about 1 dB for coupling ratio errors less than 4%, or phase errors within ±2 degrees. Adviser: Lim Nguye

ACHIEVING 1 GBPS OVER STEP-INDEX PLASTIC OPTICAL FIBER BY CONTROLLING THE EFFECTIVE NUMERICAL APERTURE

In this work, we develop a relatively simple and reliable technique to mitigate the effect of modal dispersion of standard, 1 mm step-index plastic optical fiber (SI-POF). We focus on decreasing the modal dispersion by reducing the effective numerical aperture (NA) of the fiber link. The technique involves a spatial mode filter that is constructed by using a commercially available polycarbonate capillary tube having a refractive index of 1.59, with inner and outer diameters of 1 mm and 2 mm, respectively. The capillary tube holds two pieces of 1 mm SI-POF, one comes from the transmitter and the other shorter one connects to the receiver. The two fibers are aligned by the tube and separated by an air gap. Increasing the gap width inside the tube effectively reduces the NA of the fiber link. We experimentally demonstrated an error-free 1 Gb/s over 30 m of SI-POF. The simplicity, reliability, robustness, and low cost make this technique an ideal candidate for dispersion mitigation in short range telecommunication networks. Adviser: Lim Nguye

Design and Analysis of Binary Driven Coherent M-Ary QAM Transmitter for Next Generation Optical Networks

This work presents a design for a binary driven optical square M-ary quadrature amplitude modulation (QAM) transmitter for high speed optical networks. The transmitter applies tandem quadrature phase shift keying (QPSK) modulators to eliminate the need for linear broadband amplifiers and high-resolution digital to analog converters (DACs), which are both required by conventional transmitters. The transmitter design could be scaled to any order of square M-ary QAM by simply adding more QPSK modulators in tandem. It also provides a Gray coded symbol constellation, insuring the lowest bit error rate possible during symbol recovery. We also provide the design for the coupling ratios of the optical couplers that take into account the insertion loss of the optical components, in order to generate a proper 16-QAM and 64-QAM symbol constellation with equally-spaced symbols. Additionally, we analyze the impact of coupling ratio errors as well as phase errors on the bit error rate (BER) performance and constellation diagrams. The performance is tested using the OptiSystem simulation at 50 Gbaud and under presence of additive white Gaussian noise (AWGN), which demonstrated high quality symbol constellation and a BER performance similar to theoretical expectations. For 16-QAM, a BER better than 10-4 and power penalty of about 2 dB are achieved for coupling ratio errors less than 10 %, or phase errors within ±7 degrees. The 64-QAM transmitter, on the other hand, demonstrated a BER better than 10-4 and power penalty of about 1 dB for coupling ratio errors less than 4%, or phase errors within ±2 degrees

Design and Analysis of Binary Driven Coherent M-Ary QAM Transmitter for Next Generation Optical Networks

This work presents a design for a binary driven optical square M-ary quadrature amplitude modulation (QAM) transmitter for high speed optical networks. The transmitter applies tandem quadrature phase shift keying (QPSK) modulators to eliminate the need for linear broadband amplifiers and high-resolution digital to analog converters (DACs), which are both required by conventional transmitters. The transmitter design could be scaled to any order of square M-ary QAM by simply adding more QPSK modulators in tandem. It also provides a Gray coded symbol constellation, insuring the lowest bit error rate possible during symbol recovery. We also provide the design for the coupling ratios of the optical couplers that take into account the insertion loss of the optical components, in order to generate a proper 16-QAM and 64-QAM symbol constellation with equally-spaced symbols. Additionally, we analyze the impact of coupling ratio errors as well as phase errors on the bit error rate (BER) performance and constellation diagrams. The performance is tested using the OptiSystem simulation at 50 Gbaud and under presence of additive white Gaussian noise (AWGN), which demonstrated high quality symbol constellation and a BER performance similar to theoretical expectations. For 16-QAM, a BER better than 10-4 and power penalty of about 2 dB are achieved for coupling ratio errors less than 10 %, or phase errors within ±7 degrees. The 64-QAM transmitter, on the other hand, demonstrated a BER better than 10-4 and power penalty of about 1 dB for coupling ratio errors less than 4%, or phase errors within ±2 degrees

ACHIEVING 1 GBPS OVER STEP-INDEX PLASTIC OPTICAL FIBER BY CONTROLLING THE EFFECTIVE NUMERICAL APERTURE

In this work, we develop a relatively simple and reliable technique to mitigate the effect of modal dispersion of standard, 1 mm step-index plastic optical fiber (SI-POF). We focus on decreasing the modal dispersion by reducing the effective numerical aperture (NA) of the fiber link. The technique involves a spatial mode filter that is constructed by using a commercially available polycarbonate capillary tube having a refractive index of 1.59, with inner and outer diameters of 1 mm and 2 mm, respectively. The capillary tube holds two pieces of 1 mm SI-POF, one comes from the transmitter and the other shorter one connects to the receiver. The two fibers are aligned by the tube and separated by an air gap. Increasing the gap width inside the tube effectively reduces the NA of the fiber link. We experimentally demonstrated an error-free 1 Gb/s over 30 m of SI-POF. The simplicity, reliability, robustness, and low cost make this technique an ideal candidate for dispersion mitigation in short range telecommunication networks. Adviser: Lim Nguye