We present a photonic based broadband DSSS system with photonic matched filter. The optical delay line and optical switch-based encoder/decoder is used in signal spreading/de-spreading. The simulation results show that the photonic matched filter could achieve fast acquisition of PN sequence.
A pre-distortion algorithm of generating driving signals was proposed for high-order QAM modulation based on IQ modulator. IQ modulator working in the nonlinear area and driving by non-uniform signals was employed. The pre-distorted driving signal requires lower signal-to-noise ratio than the common uniform driving signal in QAM modulation.
Broadband thermo-optic switch based on an ultra-compact W2 photonic crystal waveguide (PCW) is demonstrated with
an integrated titanium/aluminum microheater on its surface. The operating principle relies on shifting a transmission-dip
caused by the enhanced coupling between the defect modes in W2 PCW. As a result, broadband switching functionality
with larger extinction ratio can be attained. Moreover, microheaters with different width are evaluated by the power
consumptions and heating transfer efficiency, and an optimized slab microheater is utilized. Finally, switching
functionality with bandwidth up to 24 nm (1557~1581 nm) is measured by the PCW with footprint of only
8μm×17.6 μm, while the extinction ratio is in excess of 15 dB over the entire bandwidth. What’s more, the switching speed is obtained by the measurement of alternating current modulation. Response time for this thermo-optic switch is
11.0±3.0 μs for rise time and 40.3±5.3 μs for fall time, respectively.
We demonstrated and fabricated a 20μm-long ultra-compact variable optical attenuator based on thermo-optical effect
with slow light photonic crystal waveguide (PCWG). In simulation, we optimize the line-defect width and radius/period
ratio (r/a) of the PCWG for deep photonic band gap and large slope photonic band edge. An r/a=140nm/410nm W1
PCWG is selected for its -60dB depth and 36dB variable attenuation range when the tunable refractive index change is
0.01. We also study different shapes of micro-heaters for low power consumption and high heat transfer efficiency. A
24.6mW and 75.9% heat transfer efficiency are achieved in a 2μm-wide right-angle-shaped micro-heater. In experiment,
A 4.6nm red shift at the cutoff wavelength of the fundamental mode and a 10dB tunable attenuation range are achieved
through tuning the temperature of the W1 PCWG by an 4.7μm-wide aluminum micro-heater with a maximum power
consumption as low as 30.7mW.
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