Low-distortion and low-noise amplifiers for optical communication systems

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Name of the Speaker: Mrudula K (EE19D017)
Guide: Dr. Deepa Venkitesh
Venue/Online meeting link: ESB 210B
Date/Time: 19th September 2022, 3pm

It is predicted that, across the world, there would be over 7.5 billion users accessing the internet through wireless and wireline networks by 2030 []. Fiber optic communication system being the backbone for mobile data and internet traffic; this proliferation of internet usage directly translates to a corresponding increased data-rate and bandwidth requirements in access, metro and long haul fiber optic links. The high data rate is accomplished either by employing wavelength division multiplexing (WDM) or by using advanced modulation formats which utilizes amplitude, phase and polarization of the electric field to encode digital data. The use of advanced modulation formats necessitates larger signal to noise ratios for error-free detection of data. Each optical amplifier in a fiber optic link, in addition to providing optical gain, also generates noise. Thus, there is a trade-off between the achievable spectral efficiency and the link length. Modulating outside the traditional communication bands towards an ultra-wide band option is another potential solution to improve the capacity of fiber links.

Traditional erbium doped fiber amplifiers restrict the wavelengths of operation to the C- (1530-1565 nm) and the L-band (1565-1625 nm), and have typical noise figure values of > 5 dB. An alternative to doped fiber amplifiers is the use of phase sensitive amplifiers (PSA). PSAs offer the possibility of adjusting the gain spectra and reducing the noise figure to even 0 dB. Optimal choice of a nonlinear medium to be used in PSA designs that can offer noise figure better than the commercial EDFAs, with least complexity/energy consumption is a subject of investigation. Nonlinear semiconductor optical amplifiers (SOA) have an ultra-wide band gain spectrum and have the potential to be used as nonlinear medium for both PSA and ultra-wide band amplification. In this seminar, we discuss the possibility of using SOA as an amplifier and as a nonlinear medium. We also discuss the characterisation details of a dispersion oscillating fiber for its potential use as a nonlinear medium for PSA.