David M. Cutrer

Dynamic range requirements for optical transmitters in fiber-fed microcellular networks

Analog fiber-optic links can be used for antenna remoting in microcellular networks. Using a statistical model of user access in a wireless network, it is shown that by accepting a modest (<0.5%) percentage of blocked calls, a modest optical link dynamic range of 91 dB (1 Hz) is required. By using multiple fiber-fed antennas per cell and proper network protocol, the required dynamic range is dramatically reduced to <80 dB for the same blocking probability.<<ETX>>

Techniques for improving in-building radio coverage using fiber-fed distributed antenna networks

The characteristics of an in-building fiber-fed distributed antenna network are addressed by simulation of an indoor non-shadowed radio environment at 900 MHz, 1.8 and 1.9 GHz. The performance of the network is discussed in terms of the number and placement of antennas, and the method of diversity combination used. Statistical analysis of the radio environment shows that the arbitrary placement of two fiber-fed antennas in the room is as good as conventional half-wave diversity. Furthermore, the performance of multiple distributed antennas (>3) is typically superior to non-distributed architectures.

Ultralow power optical interconnect with zero-biased, ultralow threshold laser-how low a threshold is low enough?

Ultralow threshold (I/sub th/<100 /spl mu/A) lasers can be used in ultralow power optical interconnect, preferably in a bias-free digital optical modulation format. We show that even though optical power requirements for successful transmission may dictate that the pulse drive current be many times that of I/sub th/, reducing the latter to 10-100 pA is still essential in minimizing the total driver power to the laser at multi-gigabit data rates.<<ETX>>

Optical transmission of narrowband millimeter-wave signals

We describe experimentally and theoretically three techniques used to transmit narrowband millimeter-wave (MM-wave) analog signals over optical fiber: 1) narrowband MM-wave optical transmitters based on resonant modulation of monolithic semiconductor lasers, 2) feedforward optical modulation, and 3) a passively mode-locked laser operating in an optoelectronic phase-locked loop. The resonant modulation response at the cavity round-trip frequency is fully characterized for multiple-contact lasers under various bias conditions. Issues such as modulation efficiency, passband bandwidth, noise, and intermodulation distortion are addressed. A system implementation of resonant modulation is presented in which two simultaneous 2.5-Mb/s BPSK channels centered at a subcarrier frequency of 41 GHz is transmitted over 400 m of single-mode fiber. Simple microstrip matching circuits are fabricated at 41 GHz to couple the MM-wave signals into the laser. Resonant modulation of single-contact lasers is also reported. Next, implementation of a tunable MM-wave (30-300 GHz) optical transmitter based on feedforward optical modulation is presented, and the fundamental performance of this technique investigated in terms of noise and dynamic range. Feedforward modulation is used to transmit 300-Mb/s data at 39 GHz over 2.2 km of single-mode fiber. Finally, a passively mode-locked monolithic semiconductor laser operating in an optoelectronic phase-locked loop is implemented as a narrowband MM-wave optical transmitter at 46 GHz. The phase-locked loop bandwidth, MM-wave tracking capability, and fundamental limit to the stability of the MM-wave subcarrier is established. The relative merits of the three techniques are discussed and compared. The MM-wave subcarrier transmission results presented here represent the highest reported to date. >

Multichannel millimeter wave subcarrier transmission by resonant modulation of monolithic semiconductor lasers

We study the multichannel analog and digital performance of narrowband millimeter-wave optical transmitters based on resonant modulation of monolithic semiconductor lasers. Two-tone measurements are performed under various bias conditions at a cavity round-trip frequency of 41 GHz, and optical transmission over 400 m of single-mode fiber of two simultaneous 2.5 Mb/s BPSK channels centered at a subcarrier frequency of 41 GHz is demonstrated.<<ETX>>

On distributed microwave effects in semiconductor lasers and their practical implications

Recently, it has been shown that when a semiconductor laser is directly modulated at high frequencies, the modulation signals suffer substantial loss and phase shift propagating from the wire feed point along the length of the laser. It was suggested that these distributed microwave effects lead to a further bandwidth degradation in electrical current injection over the single‐pole roll‐off predicted by a lumped RC model. We show, however, that this degradation is significant only when the laser is driven directly by a voltage source. In contrast, when the laser is driven, commonly, through a 50 Ω transmission line the degradation is minimal, and the total injection current is still RC limited.

Parametric dependence of timing jitter in gain‐switched semiconductor lasers

In this letter we derive analytic results for the timing jitter in gain‐switched semiconductor lasers driven with electrical pulse shapes commonly used in practice. The analytic results allow us to identify laser parameters as well as electrical bias and pulse conditions which affect timing jitter. These results are in good agreement with experimental observations.

Resonant modulation of single contact monolithic semiconductor lasers at millimeter wave frequencies

Resonant modulation of a single contact semiconductor laser at the cavity roundtrip frequency of 40 GHz is demonstrated. Efficient mode coupling is obtained with a single contact device by utilizing the high attenuation of the millimeter‐wave modulation signal along the laser stripe. The properties and limitations of this technique are analyzed using a distributed circuit model of the laser.

Theory of resonant modulation at millimeter wave frequencies of inhomogeneously biased monolithic quantum-well lasers

We show theoretically that resonant modulation at millimeter wave frequencies of inhomogeneously biased monolithic quantum-well laser diodes provides an enhancement in the modulation efficiency of >14 dB over that of the homogeneously biased laser, accompanied by a corresponding 7 dB increase in the noise and a comparable decrease in the signal-to-intermodulation distortion. We derive simple expressions for the enhancement in the modulation efficiency, the noise and intermodulation distortion, and discuss the limits of this approach and the trade off between these quantities. The theoretical results presented here are in good agreement with recently published experimental work.<<ETX>>

Is a fiber-fed antenna network optimal for in-building wireless signal distribution?

In-building radio propagation measurements at 900 MHz are used to analyze the dynamic range requirements and optimal architecture for a distributed antenna network. The ideal performance/cost ratio for the network is found to be achieved with a low-cost hybrid fiber-coax architecture. A system design procedure and field-trial results are presented.