Microwave Photonics: Mastering the application of RF signals over fiber

Technical description

Information and communication technology (ICT) systems are expanding at an awesome pace in terms of capacity demand, number of connected end-users and required infrastructure. To cope with these rapidly increasing growth rates there is a need for a flexible, scalable and future-proof solution for seamlessly interfacing the wireless and photonic segments of communication networks.

Fig. 1. Emerging ICT applications requiring smooth transition between the fiber and wireless segments of communication infrastructures

In addition, emerging paradigms such as 5G communications the Internet of Things, car-to-car communications, wireless body and personal area networks (WB/PANs), are expected to push this pressure even further (Fig. 1). The requirements demanded by most of these scenarios calls for novel technology developments in both the physical layer and the network architectures.

RF or Microwave photonics (MWP) brings together the worlds of radiofrequency (RF) engineering and optoelectronics. It is the best-positioned technology to provide a flexible, adaptive and future-proof physical layer with unrivalled characteristics by enabling the realization of key functionalities in microwave systems, which are either complex or even not directly possible within the RF domain.

During the last 25 years, PRL members have produced pioneering work in the field of MWP. The initial activity was focused mainly in signal processing and beamforming applications using fiber-based configurations.


During the last years, our activity in MWP widened to address:

a) Novel functionalities: universal MWP signal processors, arbitrary waveform generation (AWG), Optoelectronic Oscillation (OEO), Analog to Digital Conversion (ADC), instantaneous frequency measurement (IFM), true time delay lines (TTDL) and phase shifters (PS), beamforming, radio over fiber transmission (RoF), photonic implementation of Radio Access Networks (RANs), advanced instrumentation, sensing and quantum communications

b) The incorporation of novel technology approaches to MWP: Slow light, Silicon, III-V and SiNx based integrated microwave photonics Application Specific Circuits (ASPICs) and universal processors, graphene functionalization of tunable MWP chips  and Space Division Multiplexed (SDM) MWP using multicore fibers.

PRL members have succeeded in producing seminal work in many of these new approaches and continue nowadays towards their development and integration in emerging applications such as 5G communications, the Internet of Things, and autonomous driving networks. The work includes both world-class research as well as technology transfer (patents) and creation of spin-off companies.

Many of these contributions are in collaboration with other active research lines carried within PRL. For instance and to cite a few, the recent report of the first monolithic  MWP filter has been carried together with the PRL research line in integrated optics the proposal and subsequent work on the use of multicore fibers (MCF) for MWP applications is being carried together with the PRL research line on Spatial Division Multiplexing.

The current and targeted (near future) activity in this research lines is divided into three main areas of work that address a) integrated Microwave photonics, b) Advanced Microwave Photonics Subsystems & Techniques and c) Applications, as shown in Fig. 2

Fig. 2. Current and targeted areas of activity within the MWP Research Line

PRL is equipped with last generation equipment and instrumentation for MWP measurement up to 67 GHz

We offer periodically open positions for PhD students as well as welcome international visitors for short (6 month to 1 year).


The following is a list of publications reporting landmark achievements in the field of MWP carried out by PRL researchers.


[1] J. Capmany, B. Ortega and D. Pastor, ‘A Tutorial on Microwave Photonic Filters’, (Invited Paper), IEEE J. Lightwave Technol., pp. 201-229, (2006).

[2] J. Capmany and D. Novak, ‘Microwave Photonics: combining two worlds’, Nature Photonics, vol. 1, pp. 319-330, (2007).

[3] M. Bolea, J. Mora, B. Ortega, J. Capmany, ‘Optical UWB pulse generator using an N tap microwave photonic filter and phase inversion adaptable to different pulse modulation formats’, Opt. Express, Vol. 17, Issue 7, pp. 5023-5032 (2009).

[4] W. Xue, S. Sales, J. Capmany and J. Mörk,’ Wideband 360º microwave photonic phase shifter based on slow light in semiconductor optical amplifiers’, Opt. Express, Vol. 18, Issue 6, pp.6156-6163 (2010).

[5] J. Capmany, I. Gasulla and S. Sales, ‘Microwave Photonics: Harnessing slow light’,             Nature Photonics 5 (12), pp. 731-733, (2011).

[6] I. Gasulla and J. Capmany, “Microwave Photonics applications of Multicore Fibers”, IEEE Photonics Journal, Vol. 4, pp. 877 – 888, (2012).

[7] A. Ruiz-Alba, J. Mora, W. Amaya, A. Martínez, V. Garcia-Muñoz, D. Calvo and J. Capmany, “Microwave Photonics Parallel Quantum Key Distribution”, IEEE Photonics Journal, Vol. 4, pp. 931 – 942, (2012).

[8] J. Sancho, J. Bourderionnet, J. Lloret, S. Combrié, I. Gasulla, S. Xavier, S. Sales, P. Colman, G. Lehoucq, D. Dolfi, J. Capmany & A. De Rossi, “Integrable microwave filter based on a photonic crystal delay line”, Nature Communications, Vol. 3, no. 1075, doi:10.1038/ncomms2092, (2012).

[9] D.A.I. Marpaung, C. Roeloffzen, R. Heideman, A. Leinse, S. Sales and J. Capmany, “Integrated Microwave Photonics”, Laser and Photonics Reviews, Vol. 7, pp. 506-538 (2013).

[10] J. Capmany, J. Mora, I. Gasulla, J. Sancho, J. Lloret and S. Sales, ‘Microwave Photonic Signal Processing’ (Invited), IEEE Journal Lightwave Technol., Vol. 31, pp. 571 – 586, (2013).

[11] Capmany, J., Domenech, D., Muñoz, P. “Graphene integrated microwave photonics”, IEEE J. Lightwave Technol., vol. 32, pp. 3785-3796, (2014).

[12] Daniel Pérez, Ivana Gasulla, and José Capmany, “Software-defined reconfigurable microwave photonics processor,” Opt. Express 23, 14640-14654 (2015).

[13] José Capmany, Ivana Gasulla, Daniel Pérez, “Microwave photonics: The programmable processor,” Nature Photonics, 10, pp.6-8, (2016).

[14] Fandiño, Javier S. and Muñoz, Pascual and Doménech, David and Capmany, José, “A monolithic integrated photonic microwave filter,” Nature Photonics, in press, (2017).

[15] J Hervas, AL Ricchiuti, W Li, NH Zhu, CR Fernandez-Pousa, S Sales, M Li, & J. Capmany, “Microwave Photonics for Optical Sensors,” in IEEE Journal of Selected Topics in Quantum Electronics, doi: 10.1109/JSTQE.2017.2651117

[16] B.Ortega, J.Mora, R.Chulia, “Optical beamformer for 2-D phased array antenna with subarray partitioning capability”, IEE Photonics Journal, vol. 8, no3, DOI: 10.1109/JPHOT.2016.2550323 (2016).