Anthony L. Campillo

Long-Haul Analog Photonics

A paper on long-haul analog photonics is presented using theory and experimental results. Various analog fiber-optic modulation formats are reviewed, including intensity modulation with direct detection, phase modulation with interferometric demodulation, and suppressed-carried techniques. Modulation linearization methods are reviewed. The limitations of and requirements for photodiode detectors are described.

Orthogonally polarized single sideband modulator

A modulator design capable of producing a new constant intensity modulation format is proposed. The modulator consists of a Mach-Zehnder interferometer containing two polarization modulators. By shifting the relative phase of the electrical drive signal applied to each polarization modulator by 90 degrees a modulation consisting of a carrier and a single sideband, polarized orthogonal to the carrier, is produced.

Chromatic dispersion-monitoring technique based on phase-sensitive detection

A novel chromatic dispersion-monitoring technique is proposed and demonstrated. A path imbalanced interferometer is used to monitor the intensity to phase conversion of a radio-frequency spectral component of a modulated signal. The measurement range of the technique is independent of the data rate and can be tuned by adjusting the path length difference of the interferometer. An unambiguous measurement range of >2300 ps/nm is demonstrated for a 10-GB/s nonreturn-to-zero signal.

Phase performance of an eight-channel wavelength-division-multiplexed analog-delay line

The design of an eight-channel 25 /spl mu/s wavelength-division-multiplexed (WDM) microwave photonic delay line is described. The performance of the delay line was studied by measuring the temperature dependent relative phase drift between channels and the interchannel crosstalk. A simple method for measuring the maximum phase errors produced by the interchannel crosstalk is described and used to measure the maximum error on a channel in this system. The use of polarization interleaving and dispersion compensation to reduce the effects of crosstalk in the system is examined experimentally.

Chromatic dispersion effects in analog polarization-modulated links

The effect of chromatic dispersion on a photonic link employing polarization modulation is studied analytically and experimentally. For analog polarization modulation, dispersion introduces a frequency-dependent rotation to the orientation of modulation about the center of modulation. As a result, the dispersion-limited bandwidth of the link will depend on receiver design.

Interchannel nonlinear crosstalk in analog polarization modulated WDM systems

Crosstalk in an analog polarization modulation (PolM) system is studied analytically and experimentally. It is shown capable of producing dramatically lower crosstalk levels than intensity modulation (IM) at higher modulation frequencies (greater than 1 GHz) for a system with 200 GHz channel spacing. Calculations based on the developed analytical model show excellent agreement with experimental results and allow us to determine the necessary launch conditions for low-crosstalk transmission in a polarization modulation link

Nonlinear distortion and crosstalk in microwave fiber-radio links

Dispersion and fiber nonlinearities are potentially significant sources of impairment in fiber-radio links. An experimental study of second harmonic distortion and WDM crosstalk in externally modulated microwave fiber-radio links indicates that these impairments are much more significant than previously observed at CATV frequencies below 1 GHz.

Comparison of crosstalk for amplitude and phase modulation in an analog fiber optic link

We investigated analog rf crosstalk levels in a 25 km, wavelength-division multiplexed, Er-amplified fiber optic link for both a) amplitude modulation with direct photodetection and b) phase modulation with differential interferometric demodulation and photodetection. Experimental results are presented for optical channel spacing in the range 50 GHz to 200 GHz.

Analysis of interchannel crosstalk in a dispersion-managed analog transmission link

A technique for computing the effect of cross-phase modulation (XPM) on two copropagating analog channels in an optical fiber link is presented. In this approach, the interaction between the two channels is linearized by keeping the self-phase modulation (SPM) and XPM interactions in the strong optical carrier components only at lowest order and then at the next order, deriving the effect on the modulation components of both channels when the optical carrier is strong relative to the other components of the channel. In contrast to some previously suggested approaches, it is not assumed that the pump is undistorted, and therefore, this method accurately describes distortions due to SPM, XPM, and dispersion management in both channels. This method is easily applied to systems with multiple spans employing dispersion management with loss and gain. The expressions for the received radio frequency power and crosstalk between the two channels when direct detection is used are then provided. Using this approach, new expressions for the amplitude modulation and phase modulation modes of the two channels are derived, and the way they exchange energy when SPM, XPM, and dispersion are all considered is explained. This method yields excellent agreement between theory and experimental data.

RF phase distortion due to crosstalk in an 8 channel wavelength division multiplexed analog delay line

We present experimental results of crosstalk for an eight channel WDM 25 microsecond delay line. The total phase error produced by the crosstalk onto one channel from the other seven over a frequency of 0-20 GHz is measured.