Generation of S -band WDM sources by using non-linear properties of silica fibers.
Boyraz, Ozdal
2001
Abstract
Demand for large bandwidth increases constantly by the development of Internet technology. The capacity of the erbium doped fiber amplifier (EDFA) band itself is not sufficient to satisfy this bandwidth demand and new communication windows should be opened. However, providing low cost and environmentally stable multiple wavelength sources operating beyond the EDFA band is a challenge. This thesis comprises of three techniques of generating multiple wavelength sources band generated by existing sources in the EDFA band. Additionally, these sources can operate both within the EDFA band and beyond the EDFA band with high environmental stability. All of the experimental results obtained in thesis are also confirmed by modeling and simulations. The first technique discussed in this thesis is the generation of 10 Gb/s short pulses by spectral carving of supercontinuum (SC) generated in short fibers. Particularly, the pulse quality and the coherence properties of the new sources are investigated. It is shown that since the SC is generated in short lengths, nonlinear effects like modulation instability (MI) do not degrade the coherence of the SC. Therefore, coherent short pulses as far as 60 nm away from the pump laser can be generated. The other advantages of the short fiber SC generation are defined as the large uniform bandwidth, where the 20 dB bandwidth is measured to be >140 nm with +/-0.5 uniformity over >40 nm, and high power spectral density, which is >7 dBm/nm at the uniform portion of the SC. The second technique demonstrates a novel continuous wave (CW) signal scheme generation by utilizing the longitudinal modes of the SC. The thesis shows that by this scheme >1600 channel wavelength division multiplexing (WDM) sources with precise wavelength spacing, which is set by the 10 GHz repetition rate of the pump laser, can be generated. Particularly, the noise performance of generated CW signals is investigated. The results show that the stability of the CW signals are ultimately set by the pump laser and <4dB/Hz degradation in amplitude noise is measured compared to pump laser. The last technique discuss the broad band wavelength converter to copy the existing sources in the EDFA band (C Band) to S-band (communication band with lambda < 1530 nm) or L-band (lambda > 1565 nm) by using modulational instability in fibers. Experimentally, the intrinsic limitations of this technique are determined to be channel cross talk and polarization sensitivity. By using a novel loop configuration the polarization sensitivity is decreased to less than 0.65 dB from 2.5 dB. The cross talk issue is addressed by optimizing the fiber length, and the cross talk values as low as <-27 dB is obtained.Subjects
Band Conversion Erbium-doped Fiber Amplifier Generation Linear Non Properties S-band Silica Fibers Sources Supercontinuum Using Wdm
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Thesis
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