Katarzyna Balakier

Microwave Photonic Integrated Circuits for Millimeter-Wave Wireless Communications

This paper describes the advantages that the introduction of photonic integration technologies can bring to the development of photonic-enabled wireless communications systems operating in the millimeter wave frequency range. We present two approaches for the development of dual wavelength sources for heterodyne-based millimeter wave generation realized using active/passive photonic integration technology. One approach integrates monolithically two distributed feedback semiconductor lasers along with semiconductor optical amplifiers, wavelength combiners, electro-optic modulators and broad bandwidth photodiodes. The other uses a generic photonic integration platform, developing narrow linewidth dual wavelength lasers based on arrayed waveguide gratings. Moreover, data transmission over a wireless link at a carrier wave frequency above 100 GHz is presented, in which the two lasers are free-running, and the modulation is directly applied to the single photonic chip without the requirement of any additional component.

Coherent terahertz photonics

We present a review of recent developments in THz coherent systems based on photonic local oscillators. We show that such techniques can enable the creation of highly coherent, thus highly sensitive, systems for frequencies ranging from 100 GHz to 5 THz, within an energy efficient integrated platform. We suggest that such systems could enable the THz spectrum to realize its full applications potential. To demonstrate how photonics-enabled THz systems can be realized, we review the performance of key components, show recent demonstrations of integrated platforms, and give examples of applications.

Photonic generation for multichannel THz wireless communication

We experimentally demonstrate photonic generation of a multichannel THz wireless signal at carrier frequency 200 GHz, with data rate up to 75 Gbps in QPSK modulation format, using an optical heterodyne technique and digital coherent detection. BER measurements were carried out for three subcarriers each modulated with 5 Gbaud QPSK or for two subcarriers modulated with 10 Gbaud QPSK, giving a total speed of 30 Gbps or 40 Gbps, respectively. The system evaluation was also performed with three subcarriers modulated with 12.5 Gbaud QPSK (75 Gbps total) without and with 40 km fibre transmission. The proposed system enhances the capacity of high-speed THz wireless transmission by using spectrally efficient modulated subcarriers spaced at the baud rate. This approach increases the overall transmission capacity and reduces the bandwidth requirement for electronic devices.

Optical injection locking of monolithically integrated photonic source for generation of high purity signals above 100 GHz

A monolithically integrated photonic source for tuneable mm-wave signal generation has been fabricated. The source consists of 14 active components, i.e. semiconductor lasers, amplifiers and photodetectors, all integrated on a 3 mm(2) InP chip. Heterodyne signals in the range between 85 GHz and 120 GHz with up to -10 dBm output power have been successfully generated. By optically injection locking the integrated lasers to an external optical comb source, high-spectral-purity signals at frequencies >100 GHz have been generated, with phase noise spectral density below -90 dBc/Hz being achieved at offsets from the carrier greater than 10 kHz.

Monolithically Integrated Optical Phase Lock Loop for Microwave Photonics

We present a review of the critical design aspects of monolithically integrated optical phase lock loops (OPLLs). OPLL design procedures and OPLL parameters are discussed. A technique to evaluate the gain of the closed loop operating system is introduced and experimentally validated for the first time. A dual-OPLL system, when synchronised to an optical frequency comb generator without any prior filtering of the comb lines, allows generation of high spectral purity signals at any desired frequency from several GHz up to THz range. Heterodyne phase locking was achieved at a continuously tuneable offset frequency between 2 and 6 GHz. Thanks to the photonic integration, small dimensions, and custom-made electronics, the propagation delay in the loop was less than 1.8 ns, allowing good phase noise performance with OPLLs based on lasers with linewidths less than a few MHz. The system demonstrates the potential for photonic integration to be applied in various microwave photonics applications where narrow-bandwidth tuneable optical filters with amplification functionality are required.

Tuneable monolithically integrated photonic THz heterodyne system

We report a tuneable heterodyne photonic THz source, monolithically integrated on an InP chip. The system, locked to a comb generator, allows generation of high purity signals and is tuneable from 25 GHz to 1.6 THz. Continuous frequency sweeps of 300 MHz and tuneability between comb lines from 2 GHz to 6 GHz offset are demonstrated. Due to the photonic integration and small dimension, custom-made electronics, the propagation delay in the loop was less than 1.8 ns.

Tuneability of monolithically integrated optical phase lock loop for THz generation

This work presents a monolithically integrated optical phase lock loop (OPLL) synchronised to an Optical Frequency Comb Generator (OFCG) without any prior filtering of the comb lines for the first time. The heterodyne phase locking is achieved at a tuneable offset frequency in the range of 2 to 6 GHz, while the optical comb lines are spaced by 12 GHz. This is of particular interest as it allows investigation of the influence of the nearest comb lines on OPLL performance. Moreover, the work discusses continuous tuneability limitations of a photonic THz source based on the single OPLL and proposes a solution to improve the frequency agility. Finally, the spectra of signals ranging from 2.5 up to 21.5 GHz, generated by heterodyning the locked slave laser and the subsequent comb lines, are presented and analysed. Phase noise performance of -80 dBc/Hz at 10 kHz offset across the frequency range is reported.

Microwave Photonics: Present Status and Future Outlook (Plenary Paper)

Microwave photonics is now a mature research area, the first papers in the field having been published some fifty years ago. Some application areas, such as wireless over fiber, have enjoyed major commercial success, with annual sales revenues of >

Prospects for millimetre-wave-over-fibre and THz-over-fibre systems

100 m and systems installed worldwide. Other areas, such as optical beam-forming for antennas and optical filtering for microwave systems have delivered impressive research results but have yet to find widespread application. In this paper the systems enabling capabilities of microwave photonics will be reviewed and emerging technologies that could increase the range of applications for which microwave photonics offers an attractive solution will be described.

Comparison of photonic integrated circuits for millimeter-wave signal generation between dual-wavelength sources for optical heterodyning and pulsed mode-locked lasers

Optical fibre transmission has enabled greatly increased transmission rates, with 10 Gb/s common in local area networks. End users find wireless access highly convenient, however limited spectrum availability at microwave frequencies results in per-user transmission rates which are limited to much lower values, 500 Mb/s for 5 GHz band IEEE 802.11ac, for example. Extending the high data-rate capacity of optical fibre transmission to wireless devices, requires greatly increased carrier frequencies. This paper will describe how photonic techniques can enable ultra-high capacity wireless data distribution and transmission using signals at millimetre-wave and TeraHertz (THz) frequencies.