Akhil Shah - Academia.edu (original) (raw)

Papers by Akhil Shah

Research paper thumbnail of ISI equalization for a coherent optical MIMO (COMIMO) system

Page 1. ISI Equalization for a Coherent Optical MIMO (COMIMO) System Akhil R. Shah, Rick CJ Hsu, ... more Page 1. ISI Equalization for a Coherent Optical MIMO (COMIMO) System Akhil R. Shah, Rick CJ Hsu, and Bahram Jalali Electrical Engineering Department, University of California, Los Angeles, CA 90095-1594 USA akhil137@ucla.edu ...

Research paper thumbnail of Capacity enhancement in coherent optical MIMO (COMIMO) multimode fiber links

IEEE Communications Letters, 2006

In this paper, we study a coherent optical MIMO (COMIMO) multi-mode fiber link proposed for enhan... more In this paper, we study a coherent optical MIMO (COMIMO) multi-mode fiber link proposed for enhancing the fiber information capacity. We examine the statistical characterization of the equivalent MIMO channel and the improvement in the fiber capacity due to MIMO transmission. It is shown that the equivalent channel behaves similarly to a complex Gaussian MIMO channel, suggesting that the available results on wireless MIMO communication systems can be applied to optical fiber links for capacity enhancement.

Research paper thumbnail of Adaptive equalisation for broadband predistortion linearisation of optical transmitters

Iee Proceedings-optoelectronics, 2005

Polynomial predistortion is known to have limited signal bandwidth and modulationdepth range abov... more Polynomial predistortion is known to have limited signal bandwidth and modulationdepth range above which the improvement gained by linearisation quickly diminishes. This problem has been studied for RF power amplifiers in the context of wireless communications but less so for analogue fibre optic links which could greatly benefit from a broadband, large dynamic range predistortion lineariser. Behavioural models are presented for static and dynamic nonlinearities based on the Volterra series. It is shown that for modulation frequencies much lower than the relaxation oscillation frequency, a simple predistortion architecture that employs only postfiltering is adequate to compensate for memory effects that limit predistortion bandwidth. Design considerations for an analogue adaptive tap delay line filter are also presented along with the general frequency response needed to compensate for memory. The dependence of predistortion parameters on modulation depth is analysed, and it is shown that an adaptive predistorter using instantaneous digital adaptation (IDA) provides both a larger signal-to-noise and distortion ratio (SNDR) and modulation depth range at the transmitter for a given noise floor.

Research paper thumbnail of Coherent Optical MIMO

... Bahram Jalali, Rick CJ Hsu, and Akhil R. Shah University of California, Los Angeles, Departme... more ... Bahram Jalali, Rick CJ Hsu, and Akhil R. Shah University of California, Los Angeles, Department of Electrical Engineering, Los Angeles, CA90095-1594 USA; ... 295-296, November 2002 8. L. Raddatz, D. Hardcare, IH White, RV Penty, DG Cunningham, MRT Tan, and S.-Y. Wang ...

Research paper thumbnail of Coherent Optical MIMO (COMIMO

IEEE/OSA Journal of Lightwave Technology, 2005

We present a multiple-input multiple-output (MIMO) optical link based on coherent optics and its ... more We present a multiple-input multiple-output (MIMO) optical link based on coherent optics and its ability to exploit the inherent information capacity of multimode fiber. A coherent implementation differs from previous work in optical MIMO by allowing the system to tolerate smaller modal delay spreads, because of a much larger carrier frequency, and yet maintain the necessary diversity needed for MIMO operation. Furthermore, we demonstrate the use of MIMO adaptive equalization to mitigate intersymbol interference when exceeding the bandwidth-length product of the link. The impact of phase noise is studied with numerical simulation.

Research paper thumbnail of Coherent optical MIMO (COMIMO

IEEE/OSA Journal of Lightwave Technology, 2005

We present a multiple-input multiple-output (MIMO) optical link based on coherent optics and its ... more We present a multiple-input multiple-output (MIMO) optical link based on coherent optics and its ability to exploit the inherent information capacity of multimode fiber. A coherent implementation differs from previous work in optical MIMO by allowing the system to tolerate smaller modal delay spreads, because of a much larger carrier frequency, and yet maintain the necessary diversity needed for MIMO operation. Furthermore, we demonstrate the use of MIMO adaptive equalization to mitigate intersymbol interference when exceeding the bandwidth-length product of the link. The impact of phase noise is studied with numerical simulation.

Research paper thumbnail of Coherent optical MIMO (Invited Paper

In this paper we present a Coherent Optical Multiple-Input Multiple-Output (COMIMO) communication... more In this paper we present a Coherent Optical Multiple-Input Multiple-Output (COMIMO) communication system and its ability to exploit the inherent information capacity of Multi-Mode Fiber (MMF). COMIMO technique is a promising approach to unlock the information capacity of MMF as it ensures the necessary diversity for practically any fiber length. When exceeding the bandwidth-length product of the link, MIMO adaptive

Research paper thumbnail of Coherent Optical Multiple-Input Multiple-Output communication

Ieice Electronic Express, 2004

Abslrocf-It is shown that coherent optical implementation is crucial for an optical multiple-inpu... more Abslrocf-It is shown that coherent optical implementation is crucial for an optical multiple-input multiple-output (MIMO) system to work. It ensures successfnl channel separation for practically any data rate or fiher length.

Research paper thumbnail of Coherent optical multiple-input multiple-output communication over multimode fiber

Abslrocf-It is shown that coherent optical implementation is crucial for an optical multiple-inpu... more Abslrocf-It is shown that coherent optical implementation is crucial for an optical multiple-input multiple-output (MIMO) system to work. It ensures successfnl channel separation for practically any data rate or fiher length.

Research paper thumbnail of ISI equalization for a coherent optical MIMO (COMIMO) system

Page 1. ISI Equalization for a Coherent Optical MIMO (COMIMO) System Akhil R. Shah, Rick CJ Hsu, ... more Page 1. ISI Equalization for a Coherent Optical MIMO (COMIMO) System Akhil R. Shah, Rick CJ Hsu, and Bahram Jalali Electrical Engineering Department, University of California, Los Angeles, CA 90095-1594 USA akhil137@ucla.edu ...

Research paper thumbnail of Capacity enhancement in coherent optical MIMO (COMIMO) multimode fiber links

IEEE Communications Letters, 2006

In this paper, we study a coherent optical MIMO (COMIMO) multi-mode fiber link proposed for enhan... more In this paper, we study a coherent optical MIMO (COMIMO) multi-mode fiber link proposed for enhancing the fiber information capacity. We examine the statistical characterization of the equivalent MIMO channel and the improvement in the fiber capacity due to MIMO transmission. It is shown that the equivalent channel behaves similarly to a complex Gaussian MIMO channel, suggesting that the available results on wireless MIMO communication systems can be applied to optical fiber links for capacity enhancement.

Research paper thumbnail of Adaptive equalisation for broadband predistortion linearisation of optical transmitters

Iee Proceedings-optoelectronics, 2005

Polynomial predistortion is known to have limited signal bandwidth and modulationdepth range abov... more Polynomial predistortion is known to have limited signal bandwidth and modulationdepth range above which the improvement gained by linearisation quickly diminishes. This problem has been studied for RF power amplifiers in the context of wireless communications but less so for analogue fibre optic links which could greatly benefit from a broadband, large dynamic range predistortion lineariser. Behavioural models are presented for static and dynamic nonlinearities based on the Volterra series. It is shown that for modulation frequencies much lower than the relaxation oscillation frequency, a simple predistortion architecture that employs only postfiltering is adequate to compensate for memory effects that limit predistortion bandwidth. Design considerations for an analogue adaptive tap delay line filter are also presented along with the general frequency response needed to compensate for memory. The dependence of predistortion parameters on modulation depth is analysed, and it is shown that an adaptive predistorter using instantaneous digital adaptation (IDA) provides both a larger signal-to-noise and distortion ratio (SNDR) and modulation depth range at the transmitter for a given noise floor.

Research paper thumbnail of Coherent Optical MIMO

... Bahram Jalali, Rick CJ Hsu, and Akhil R. Shah University of California, Los Angeles, Departme... more ... Bahram Jalali, Rick CJ Hsu, and Akhil R. Shah University of California, Los Angeles, Department of Electrical Engineering, Los Angeles, CA90095-1594 USA; ... 295-296, November 2002 8. L. Raddatz, D. Hardcare, IH White, RV Penty, DG Cunningham, MRT Tan, and S.-Y. Wang ...

Research paper thumbnail of Coherent Optical MIMO (COMIMO

IEEE/OSA Journal of Lightwave Technology, 2005

We present a multiple-input multiple-output (MIMO) optical link based on coherent optics and its ... more We present a multiple-input multiple-output (MIMO) optical link based on coherent optics and its ability to exploit the inherent information capacity of multimode fiber. A coherent implementation differs from previous work in optical MIMO by allowing the system to tolerate smaller modal delay spreads, because of a much larger carrier frequency, and yet maintain the necessary diversity needed for MIMO operation. Furthermore, we demonstrate the use of MIMO adaptive equalization to mitigate intersymbol interference when exceeding the bandwidth-length product of the link. The impact of phase noise is studied with numerical simulation.

Research paper thumbnail of Coherent optical MIMO (COMIMO

IEEE/OSA Journal of Lightwave Technology, 2005

We present a multiple-input multiple-output (MIMO) optical link based on coherent optics and its ... more We present a multiple-input multiple-output (MIMO) optical link based on coherent optics and its ability to exploit the inherent information capacity of multimode fiber. A coherent implementation differs from previous work in optical MIMO by allowing the system to tolerate smaller modal delay spreads, because of a much larger carrier frequency, and yet maintain the necessary diversity needed for MIMO operation. Furthermore, we demonstrate the use of MIMO adaptive equalization to mitigate intersymbol interference when exceeding the bandwidth-length product of the link. The impact of phase noise is studied with numerical simulation.

Research paper thumbnail of Coherent optical MIMO (Invited Paper

In this paper we present a Coherent Optical Multiple-Input Multiple-Output (COMIMO) communication... more In this paper we present a Coherent Optical Multiple-Input Multiple-Output (COMIMO) communication system and its ability to exploit the inherent information capacity of Multi-Mode Fiber (MMF). COMIMO technique is a promising approach to unlock the information capacity of MMF as it ensures the necessary diversity for practically any fiber length. When exceeding the bandwidth-length product of the link, MIMO adaptive

Research paper thumbnail of Coherent Optical Multiple-Input Multiple-Output communication

Ieice Electronic Express, 2004

Abslrocf-It is shown that coherent optical implementation is crucial for an optical multiple-inpu... more Abslrocf-It is shown that coherent optical implementation is crucial for an optical multiple-input multiple-output (MIMO) system to work. It ensures successfnl channel separation for practically any data rate or fiher length.

Research paper thumbnail of Coherent optical multiple-input multiple-output communication over multimode fiber

Abslrocf-It is shown that coherent optical implementation is crucial for an optical multiple-inpu... more Abslrocf-It is shown that coherent optical implementation is crucial for an optical multiple-input multiple-output (MIMO) system to work. It ensures successfnl channel separation for practically any data rate or fiher length.