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Title: Novel optical communications and imaging enabled by CMOS interfaced LED technology
Author: Griffiths, Alexander D.
ISNI:       0000 0004 7431 4870
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2018
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Arrays of micron sized light-emitting diodes (micro-LEDs) allow high-frequency spatial and temporal modulation of an optical signal. Contacting micro-LED arrays to complementary metal-oxide-semiconductor (CMOS) electronics provides a mm-chip-scale device with a high level of control over the optical emission through digital input. Such devices enable novel forms of optical communication and imaging to be investigated. This thesis first demonstrates the use of CMOS controlled micro-LEDs in multi-level intensity modulated optical communications. By generating signals in a discrete fashion with weighted groups of pixels in an array, the non-linearity issues of single LED elements can be avoided and the device functions as a digital-to-light converter. Pulse amplitude modulation and discrete orthogonal frequency division multiplexing were performed, yielding data rates up to 200 Mb/s, and spectral efficiencies up to 3.96 bits/s/Hz. A novel form of optical communications is introduced where data is sent through modulation of the temporal correlation of a pulsed optical signal. Utilising single-photon detection at the receiver enables transmission at low received power levels, on the order of picowatts. While data rates prove to be modest, the scheme is robust to both constant and modulated background signals. Additionally, the implementation requires only simple semiconductor components, exhibits low electrical power consumption, and has been demonstrated under power from a nanosatellite simulation testbed. The pulse correlation approach also presents opportunities in imaging. Received signals are dependent on optical power; therefore, if relative emitted power from multiple transmitters is known, information on the reectance or absorption of an intermediate material can be obtained. This potentially enables colour or hyperspectral imaging with single-photon detectors by temporally structuring light sources. Proof-of-principle experiments have been performed using commercially available LEDs of 10 different wavelengths and printed colour targets.
Supervisor: Dawson, Martin Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral