Nikola Alic

Thermal and Kerr nonlinear properties of plasma-deposited silicon nitride/silicon dioxide waveguides

We introduce and present experimental evaluations of loss and nonlinear optical response in a waveguide and an optical resonator, both implemented with a silicon nitride/ silicon dioxide material platform prepared by plasma-enhanced chemical vapor deposition with dual frequency reactors that significantly reduce the stress and the consequent loss of the devices. We measure a relatively small loss of approximately 4dB/cm in the waveguides. The fabricated ring resonators in add-drop and all-pass arrangements demonstrate quality factors of Q=12,900 and 35,600. The resonators are used to measure both the thermal and ultrafast Kerr nonlinearities. The measured thermal nonlinearity is larger than expected, which is attributed to slower heat dissipation in the plasma-deposited silicon dioxide film. The n2 for silicon nitride that is unknown in the literature is measured, for the first time, as 2.4 x 10(-15)cm(2)/W, which is 10 times larger than that for silicon dioxide.

Time-domain waveform processing by chromatic dispersion for temporal shaping of optical pulses

We describe a novel method for subpicosecond pulse shaping based on longitudinal spectral decomposition in dispersive media. The entire system is created with standard telecommunications equipment allowing for integration with optical communication networks. The technique has the potential for time–bandwidth products ⩾104 due to exclusive reliance on time-domain processing. We introduce the principle of operation and subsequently support it with results from our experimental system. Both theory and experiments suggest third-order dispersion as the principle limitation to realizing a large number of resolvable spots. Chirped fiber Bragg gratings offer a route to increase the time–bandwidth product for high-speed signal processing applications.

Receiver structure trade-offs in equalized high-speed fiber-optic links

We experimentally investigate receiver structure trade-offs for equalized OC-192 fiber-optic links relying on Viterbi-algorithm-based sequence estimation. Our results prove that energy detection provides better performance than few-samples-per-bit detection at shorter distances of propagation. Alternatively, few-samples-per-bit detection provides longer reach at the cost of over-sampling and substantial power penalty for smaller amounts of accumulated dispersion

Dispersion Characterization of Highly Nonlinear Fiber Over a 700-nm Band

We demonstrate a new method for wideband dispersion characterization of highly nonlinear fibers with very low dispersion. The new method uses a wideband supercontinuum source and a balanced Mach-Zehnder interferometer architecture. The new dispersion reconstruction algorithm allowed dispersive measurement accuracy of 0.05 ps/km-nm over a 700-nm spectral band for standard (sloped) highly nonlinear fiber.

Modeling of Coherent and Incoherent Rayleigh Crosstalk in Conventional Optical Links

Performance of Rayleigh-dominated transmission is modeled using approximated and exact noise power spectral densities (PSDs) and results are compared to experimental measurements for nonreturn-to-zero, return-to-zero, and duobinary modulation formats. Both models accurately predict penalties associated with coherent Rayleigh crosstalk for all three formats with typical accuracy within 1 dB. For incoherent Rayleigh crosstalk, the numerical model using exact PSDs improves prediction accuracy by as much as 4 dB over the analytic model. The large, previously unexplained disagreement is attributed to the set of analytic approximations. Our results indicate that a rigorous description of the channel spectrum should be used when calculating impairments caused by incoherent Rayleigh crosstalk, particularly in very dense wavelength-division-multiplexed systems requiring a narrow optical filtering.