In this edition of the  “Photonics Worldwide – This is my Lab” column, we would like to introduce you to Benjamin Crockett and Sameer Ahmad Mir from Canada and India, respectively. Benjamin works on optical signal processing and has provided a modern reinterpretation of the Talbot effect for noise mitigation at INRS, Canada. Sameer is working on high-speed optical communication systems and has developed a novel signal processing scheme to equalize the effect of IQ imbalance transceiver impairment at IIT Madras, India. 

If you are a Ph.D. student or an early career researcher and would like the opportunity to be featured in this column, please reach out to me.

Amol Delmade

My name is Benjamin Crockett, and I am a Ph.D. student at the National Institute of Scientific Research (Institut National de la recherche scientific, INRS) near Montréal, in the province of Québec in eastern Canada. It is a great city to visit and live in due to its abundance of parks, culture and friendly people. My general field of research concerns optical signal processing and the development of new techniques to improve our access to the information contained in optical signals. I did my B.Sc. in Physics at McGill University, with a focus on condensed matter. In the end, I think my passion for music oriented me toward the wavy and Fourier subjects of photonics which eventually became my Ph.D. topic. Currently, I am working with Prof. José Azaña towards the development of noise mitigation schemes as well as novel techniques for time-frequency analysis and processing of optical signals.

     The noise mitigation scheme we recently developed is based on a modern reinterpretation of an optical effect observed in the 1800s, the Talbot effect. In our reinterpretation, the energy of a signal is redistributed into a series of peaks causing a kind of coherent loss-less sampling effect such that a signal can be effectively extracted from noise. Even more recently, we saw opportunities to extend these principles to obtain the time-frequency representation of an incoming signal directly in the optical domain, which is a very exciting and quickly evolving topic. The implementations I am working on typically involve linear devices to manipulate light, such as electro-optic phase modulators and dispersive media, which are ideal for processing both classical and quantum waves due to the inherent low loss and energy-efficient properties of these types of devices. 

    I like to work on techniques which can be interesting from a fundamental and mathematical point of view, involving concepts such as number theory and time-frequency analysis, while also providing practical solutions to real problems in fields like biology, sensing, astronomy, telecommunication and spectroscopy. I think signal processing is a relatively abstract topic of conceptual and mathematical interest and this is a very fascinating aspect for me. I believe signal processing is truly essential for multiple fields that involve information processing – which is a task that is required by virtually all areas of science and technology. 

I am Sameer Ahmad Mir, a Ph.D. candidate working on high-speed optical communication methods in Prof. Deepa Venkites’s group at the Indian Institute of Technology (IIT) Madras, Chennai, India. I graduated with a B.Tech degree from Baba Ghulam Shah Badshah University in Jammu and Kashmir, India, with a baccalaureate thesis focusing on visible light communication (Li-Fi). Since then, I have been keen on pursuing research on topics related to communications and associated signal processing, especially for high-speed light-based communication. I was among the few selected to pursue a direct Ph.D. at IIT Madras and received a fellowship from the Government of India.

My current work, at the Optical Communication Engineering and Networks Lab (OCEAN Lab) in the department of Electrical Engineering of IIT Madras, is focused on ways to increase the capacity of optical transmission systems beyond Terabits per second. This can be achieved by increasing the signal modulation levels to encode more bits in one symbol and employing higher transmission speeds (symbol rate) to improve overall information throughput. However, the performance of such advanced modulation formats and especially at symbol rates deteriorates due to transceiver impairment. I work on developing novel digital signal processing algorithms to overcome the effect of these impairments and achieve reliable data transmission. I’ve developed an adaptive constellation referencing signal processing scheme and a geometric parameter extraction method to equalize the effect of IQ imbalance impairment that originates in the optical transmitter and receiver, respectively. The former algorithm works independent of the modulation format and exhibits low complexity compared to existing algorithms and the latter algorithm intelligently adapts itself to accommodate certain levels of imbalance. The use of these algorithms can lead to efficient low-energy/bit ASIC deployment. I also like to channel my energy toward communicating science and inspire the young generation through IIT Madras Optica Student Chapter, which I am presiding.