Phil A. Davies

Efficient generation of guided millimeter-wave power by photomixing

A 70-GHz bandwidth commercial photodiode has been coupled to W-band waveguide and used as a photomixing source from 75 to 170 GHz. Maximum power conversion efficiency of 1.8% was obtained at 75 GHz, where an optical input of +10 dBm yielded a nonsaturated millimeter-wave (mm-wave) power of -7.5 dBm. Optimizing the photomixer backshort tuning at individual frequencies showed that the mm-wave power decreased with frequency to a level of -30 dBm at 170 GHz. Fixed tuning allowed the generation of power across the full waveguide band from 75 to 110 GHz, with a variation within 5 dB across the majority of the band.

Transmission of 60-GHz signals over 100 km of optical fiber using a dual-mode semiconductor laser source

High-purity 60-GHz signals, generated using a dual-mode DFB semiconductor laser, have been transmitted over 100 km of standard optical fiber with no observable degradation in purity. This device is shown to be a simple and compact optical source of high-purity 60-GHz signals for long-reach fiber-fed millimeter-wave radio systems.

High-purity millimetre-wave photonic local oscillator generation and delivery

Tunable millimetre wave generation by spectrally slicing a phase modulated lightwave is demonstrated. The low phase noise signal (-95 dBc/Hz at 100 kHz offset) can be delivered through a 9 km fibre link, with no noticeable power penalty.

Characterization of planar optical waveguides formed by copper–sodium, electric field assisted, ion exchange in glass

Planar waveguides have been formed by the electric field assisted diffusion of copper ions from a metallic copper film into a borosilicate glass (Corning 7740). The waveguides have been analysed using conventional prism coupling techniques and have been compared with the electric field assisted diffusion of silver into the same glass type. The measured refractive index profiles for copper guides are shown to have nearly Fermi function shapes, which are consistent with the theory of field assisted ion diffusion in glass. It is shown, however, that the guide depth formed by copper or silver ions is larger than that predicted by calculations based on the nominal composition, possibly indicating that only a fraction of the sodium ions within the glass are mobile. Annealing experiments have been performed on the guides in order to determine the copper self-diffusion coefficient in the glass. The coefficients are extracted from the data by fitting a non-linear diffusion equation model of ion motion in glass to the experimental profiles.

High Performance Optical Receiver Using a PIN Photodiode and Amplifier for Operation in the Millimeter-wave Region

A highly efficient photodiode plus amplifier hybrid module in the mm-wave region is demonstrated. The design uses a broadband edge-coupled PIN photodiode and a MMIC amplifier interconnected through a microstrip matching circuit. An improvement of 9 dB in output power is demonstrated at 27 GHz compared to the same PIN diode connected to a 5O¿ amplifier without matching.

Effects of extra low‐frequency noise injection on microwave signals generated by a gain‐switched semiconductor laser

Low‐frequency upconverted noise (1/f laser intensity noise and the low‐frequency noise of the driver source) has been identified as the dominant noise generation mechanism in microwave signals generated by a Fabry–Perot gain‐switched semiconductor laser. An experimental investigation is carried out using extra low‐frequency noise injection added to the drive signal. Results show the dependence of the broadband intensity noise level, formed by the overlapping of the upconverted noise sidebands present at each harmonic, on gain‐switching input parameters.

Generation of 2 THz Span Optical Comb in a Tunable Fiber Ring Based Optical Frequency Comb Generator

The generation of a 2 THz span optical comb, defined within a 10 dB power envelope and consisting of 200 optical comb lines, all stronger than -20 dBm without amplification, is reported. The effective transmittance of the generator is 11.5 dB. The comb line spacing can be adjusted with a step frequency that equals an integer multiple of 12.500 MHz while maintaining the comb profile. High coherence between the comb lines is achieved, with the bent signal between the comb lines having a noise level of -92 dBc/Hz at 1 kHz offset, and phase noise of -130 dBc/Hz at 1 MHz offset.

Polarization Mode Noise in Ultra-low Drift Phase Reference Distribution System over a Fiber Network

The impact of polarization mode noise on the temporal drift of a delivered analogue phase reference signal through an optical fiber network is studied. The relationship between the dispersion of the state of polarization, change of the state of polarization and the maximum temporal drift of the LO signal is established. The resulting temporal drift can be larger than the PMD value of the receiver under certain conditions. It is a significant contributor to the temporal drift in the ultra-low drift phase reference distribution system, especially when motion of the fiber has to be present in the system.

Millimetre wave generation by filtering the FM-IM spectra of a directly modulated DFB laser

The nonlinear characteristics of semiconductor lasers have been exploited in order to generate low phase noise microwave and millimetre-wave frequencies for radio-over-fibre applications. This is achieved using the modulation characteristics of a MQW-DFB semiconductor laser. A high FM index MQW-DFB laser is directly modulated at the resonant frequency of its FM characteristic response in order generate high order harmonics. By optimising the rf modulation frequency drive power, high order sideband components can be generated, selected and mixed on a photodetector to generate microwave and millimetre-wave frequencies. This paper presents results utilising the direct modulation technique, which demonstrate the generation of beat frequencies up to 25 GHz. Optimization of the optical filtering process and of the phase-noise dependence of the generated beat frequency on the modulation drive source are also discussed.

Prime sequences for asynchronous pulse repetition interval agile radar

We propose the use of prime sequences in pulse repetition agile radar to increase the immunity of the radar to reconnaissance and deceptive jamming. The prime sequences are mapped into state agile mapped (SAM) sequences and are used to determine the pulse repetition interval (PRI) of the radar. We show that this produces a system with low mutual interference between radars and with a low probability of ambiguous range measurement resulting in good resistance to active deceptive jamming.