Meeting the ever increasing demand for transmission capacity in wireless networks will require evolving towards higher regions in the radiofrequency spectrum, reducing cell sizes as well as resorting to more compact, agile and power efficient equipment at the base stations, capable of smoothly interfacing the radio and fiber segments. Photonic chips with fully functional microwave photonic systems are promising candidates to achieve these targets. Over the last years, many integrated microwave photonic chips have been reported in different technologies. However, and to the best of our knowledge, none of them have fully integrated all the required active and passive components. Here, we report the first ever demonstration of a microwave photonics tunable filter completely integrated in an Indium Phosphide chip and packaged. The chip implements a reconfigurable RF-photonic filter, it includes all the required elements, such as lasers, modulators and photodetectors, and its response can be tuned by means of control electric currents. This demonstration is a fundamental step towards the feasibility of compact and fully programmable integrated microwave photonic processors.Emerging information technology scenarios, such as 5G mobile communications and Internet of Things (IoT), will require a flexible, scalable and future-proof solution capable for seamlessly interfacing the wireless and fiber segments of communication networks [1,2,3]. Microwave photonics (MWP) [4,5],the interdisciplin ary approach that combines radiofrequency and photonic systems, is the best positioned technology to achieve this target. A very relevant example is 5G wireless communications, which targets an extremely ambitious range of requirements including [6,7], a 1000-fold increase in capacity, connectivity for over 1 billion users, strict latency control, as well as network flexibility via agile software programming. These objectives call for a paradigm shift in the access network to incorporate smaller cells, exploit the millimeter wave regions of the radiofrequency spectrum and implement massive multiple-input multiple-output at the base stations (BTSs) [7]. The successful integration of the wireless and fiber segments thus relies on the possibility of implementing agile and reconfigurable MWP subsystems, featuring broadband operation, as well as low space, weight and power consumption metrics. The solution consists in resorting to integrated microwave photonics (IMWP) [8,9] chips allocated either in the BTS and/or the central office in combination with radio over fiber transmission in the fiber segment connecting them [10,11]. The two fundamental issues to be solved in IMWP are related respectively to technology and architecture. First, there is the need to identify the best material platform where to implement MWP chips. Second, whether it would be better to follow an application specific photonic integrated circuit (ASPIC) approach, where a specific architecture is employed to implement a specific functionality, or to resort to a ...

Muñoz Muñoz, P. (2013). Photonics-based microwave frequency measurement using a double-sideband suppressed-carrier modulation and an InP integrated ring-assisted Mach Zehnder interferometer filter. Optics Letters. 38(21):4316-4319.

We report the design, fabrication and characterization of an integrated frequency discriminator on InP technology for microwave photonic phase modulated links. The optical chip is, to the best of our knowledge, the first reported in an active platform and the first to include the optical detectors. The discriminator, designed as a linear filter in intensity, features preliminary SFDR values the range between 67 and 79 dB.Hz(2/3) for signal frequencies in the range of 5-9 GHz limited, in principle, by the high value of the optical losses arising from the use of several free space coupling devices in our experimental setup. As discussed, these losses can be readily reduced by the use of integrated spot-size converters improving the SFDR by 17.3 dB (84-96 dB.Hz(2/3)). Further increase up to a range of (104-116 dB.Hz(2/3)) is possible by reducing the system noise eliminating the EDFA employed in the setup and using a commercially available laser source providing higher output power and lower relative intensity noise. Other paths for improvement requiring a filter redesign to be linear in the optical field are also discussed.

In this paper we present the design, manufacturing, characterization and analysis of the coupling ratio spectral response for Multimode Interference (MMI) couplers in Silicon-on-Insulator (SOI) technology. The couplers were designed using a Si rib waveguide with SiO2 cladding, on a regular 220 nm film and 2 µm buried oxide SOI wafer. A set of eight different designs, three canonical and five using a widened/narrowed coupler body, have been subject of study, with coupling ratios 50:50, 85:15 and 72:28 for the former, and 95:05, 85:15, 75:25, 65:35 and 55:45 for the latter. Two wafers of devices were fabricated, using two different etch depths for the rib waveguides. A set of six dies, three per wafer, whose line metrology matched the design, were retained for characterization. The coupling ratios obtained in the experimental results match, with little deviations, the design targets for a wavelength range between 1525 and 1575 nm, as inferred from spectral measurements and statistical analyses. Excess loss for all the devices is conservatively estimated to be less than approximately 2 dB. All the design parameters, body width and length, input/output positions and widths, and tapers dimensions are disclosed for reference.

Abstract-Instantaneous frequency measurement receivers are a well-established technology that is used for the ultrafast characterization of pulsed microwave signals over a broad bandwidth. Recently, numerous photonic approaches to instantaneous frequency measurement (IFM) have been proposed and experimentally demonstrated, with the ultimate aim of leveraging the benefits of optical technology to improve the performance of already existent electronic solutions. Despite the numerous results, not so much attention has been paid so far to understand the subtle implications that system imperfections can have on realistic photonics-based IFM receivers. Here, we focus our attention in one of the most promising among these IFM techniques, which is based in optical power monitoring of a dual-sideband suppressedcarrier modulation after a Mach-Zehnder interferometer (MZI) filter. We develop a time domain model for the rigorous analysis of all major optical and electrical effects, including amplitude imbalance and phase errors in the modulator and the MZI, as well as on-pulse RF phase/frequency modulation. Simulations are then used to illustrate the substantial effect that a non-perfectly suppressed optical carrier can have on system performance. More importantly, it is shown that in a non-ideal situation the system amplitude comparison function critically depends with input RF power, thus greatly limiting the dynamic range of the photonicsbased receiver. Some approaches to solve these issues are also discussed.