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Frequency Offset Locked, Dual Carrier Excitation of Phase modulated, Electro-optic Frequency Combs for Bandwidth Scaling and Nonlinear Spectral Broadening

Nagarjun, KP and Vikram, BS and Prakash, Roopa and Suparna, S and Singh, Ajay and Selvaraja, Shankar Kumar and Supradeepa, VR (2018) Frequency Offset Locked, Dual Carrier Excitation of Phase modulated, Electro-optic Frequency Combs for Bandwidth Scaling and Nonlinear Spectral Broadening. In: NEXT-GENERATION OPTICAL COMMUNICATION: COMPONENTS, SUB-SYSTEMS, AND SYSTEMS VII, JAN 29-31, 2018, INDIA.

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Official URL: https://doi.org/10.1117/12.2290148


DWDM with/without superchannel based photonic networks require the use of optical carriers with equalised amplitudes and frequency stabilization of adjacent carriers to realise reliable high bandwidth optical communication systems with high spectral efficiency and long reach. Cascading of electro-optic (EO) modulators is a versatile method for generating tuneable, high repetition rate frequency combs which can be used as sources for the carriers. However, the number of lines produced with this technique is limited by the number of phase modulators. Nonlinear spectral broadening is an attractive option for bandwidth scaling; however, bandwidth scaling of single carrier combs through four wave mixing suffers from unequal comb lines or power limitations due to Brillouin scattering. A simpler technique to increase the number of comb lines would involve using multicarrier excitations for comb generation which would result in a proportional increase in the comb lines. Further, dual-carrier excitation enables an excellent temporal profile for nonlinear spectral broadening. However, since the two carriers have uncorrelated drifts, the resultant frequency combs would be unsuitable for most applications. This issue can be overcome by frequency offset locking the two lasers. Here, we demonstrate frequency offset locking (MHz accuracy) of two diode lasers spaced by 100GHz by using an optical phase locked loop which locks one laser to a RF harmonic of the other. This allows for the generation of frequency comb lines locked to each other even post nonlinear broadening. Using this technique, we demonstrate a 25GHz frequency comb with >90 lines (2THz) in the C-band.

Item Type: Conference Paper
Series.: Proceedings of SPIE
Additional Information: Conference on Next-Generation Optical Communication - Components, Sub-Systems, and Systems VII, San Francisco, CA, JAN 29-31, 2018
Keywords: optical frequency combs; optical phase lock loops; DWDM; phase modulators
Department/Centre: Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering
Date Deposited: 05 Jan 2019 14:43
Last Modified: 05 Jan 2019 14:43
URI: http://eprints.iisc.ac.in/id/eprint/61260

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