Abdulamir Ali

Spectral Efficiency and Receiver Sensitivity in Direct Detection Optical-OFDM

We show by analysis and simulation that by proper biasing of the optical modulator, the intermodulation distortion is minimized. Thus the spectral efficiency can be improved and receiver sensitivity can be exchanged against spectral width.

Impact of Modulator Bias on the OSNR Requirement of Direct-Detection Optical OFDM

In optical orthogonal frequency-division multiplexing (OFDM) with direct detection, modulator bias voltage has a significant impact on receiver sensitivity. It is a compromise between control of carrier power and nonlinear distortion of the OFDM signal. In this letter, sensitivity improvement due to reduction of carrier power is treated analytically. Its range of validity is examined by simulation. The impact of nonlinearity is identified as the difference in sensitivity between a linear and a nonlinear model.

Constant envelope optical OFDM for improved nonlinear and phase noise tolerance

We introduce a new concept of OFDM transmission with constant envelope and coherent detection to reduce the sensitivity of OFDM signals to nonlinear effects and phase noise.

OFDM transceiver design for optimizing sensitivity and long-haul performance

Design parameters for optical OFDM transceivers based on intensity modulation and direct detection are considered. Proper selection of modulator bias improves sensitivity by several dB. The length of the guard interval is adapted for uncompensated long-haul transmission.

Orthogonal Frequency Division Multiplexing (OFDM) and other Advanced Options to achieve 100Gb/s Ethernet Transmission

Based on the demand for transmission technologies offering high ratio of bits per symbol, two promising candidates to achieve a data rate of 100 Gb/s per optical carrier are discussed, namely optical orthogonal frequency division multiplexing and 16-ary multilevel modulation.

Design considerations and performance comparison of high-order modulation formats using OFDM

This paper addresses OFDM transmission over optical links with high spectral efficiency, i.e. by using high-order QAM-modulation schemes as a mapping method prior to the OFDM multicarrier representation. Low and moderate cost optics which is mandatory in access and in metro applications is assumed. Here we address especially direct detection receivers using photo detectors without the need for local lasers at the transmitter side.

Experimental IM/DD OFDMA transmission with scalable receiver frontend for PON scenarios

We propose a technique to reduce the electrical hardware effort in an OFDMA-PON by reducing the ADC and DSP complexity and therefore the costs of the ONUs and show its feasibility experimentally.

Orthogonal frequency division multiplexing (OFDM) in optical communications with direct detection for metro networks

The paper addresses OFDM transmission over optical links with low and moderate cost optics which is mandatory in access and in metro applications. Here we address especially direct detection receivers using photo detectors without the need for local lasers at the transmitter side. Thus the transmission becomes nonlinear due to the magnitude squared envelope detection which requires attention when used in dispersive fibre links. We consider several solutions to overcome this problem and we optimize the transceiver design.

OFDM remodulation for 10-Gb/s/channel WDM-PON with simple carrier extraction and enhanced tolerance to Rayleigh noise

A novel OFDM-remodulation scheme for 10-Gb/s/channel WDM-PON is proposed and numerically investigated. Negative remodulation penalty is achieved without using any ultra-narrow filter or coherent detection. 40-km single-fiber bidirectional transmission is confirmed with 7-dB power margin.

Bit and power loading for optical IM/DD transmission

Orthogonal Frequency Division Multiplexing (OFDM) is an established technique for equalization of the dispersion-dominated fiber-optical channel. The dispersive nature of the optical channel results in a frequency selective equivalent channel if double sideband (DSB) intensity modulation (IM) and direct detection (DD) is employed. In order to maintain the allpass nature of the physical channel, sideband suppression using optical filters has to be applied. We will show that by use of bit and power loading, this optical filter can be rendered unnecessary.