Abstract
Abstract We present a polarization-independent tunable optical filter with variable bandwidth based on silicon-on-insulator (SOI) waveguides. The polarization-independent operation is achieved through the use of a polarization splitter-rotator and a polarization rotator-combiner, which are based on a bilevel adiabatic taper and an asymmetric directional coupler. Two stages of second-order microring resonators (MRRs) with different radii are used to achieve wavelength filtering with variable bandwidth and large free spectral range (FSR). Each stage of the second-order MRRs has a flat-top spectrum. The central wavelength of the filter is tuned by synchronous tuning of the two stages. The 3 dB bandwidth is adjusted via intentional misalignment of the passbands of the two stages. We demonstrate a prototype of such an optical filter on the SOI platform. The FSR of the fabricated device is about 90 nm. We show the tuning of the central wavelength from 1460 to 1550 nm. We adjust the 3 dB bandwidth from 37.5 to 100 GHz with a step of 12.5 GHz, with the overall insertion loss varying from −5.4 to −7.9 dB.
Highlights
As the volume of data from mobile terminals and datacenters increases rapidly, the traffic in core and metro networks is becoming more dynamic
We show the tuning of the central wavelength from 1460 to 1550 nm
We have proposed and demonstrated a polarization-independent tunable optical filter with variable 3 dB bandwidth based on SOI waveguides
Summary
As the volume of data from mobile terminals and datacenters increases rapidly, the traffic in core and metro networks is becoming more dynamic. Wang et al.: Polarization-independent tunable optical filter with variable bandwidth with an insertion loss (IL) of about −20 dB Another integrated scheme based on asymmetric MZI loaded with a pair of all-pass MRRs can realize bandwidth and central wavelength tuning simultaneously, with the tuning range of about 20 nm in the C band [12]. For the wavelength filtering part, we use two serially cascaded second-order MRRs to realize the wavelength and bandwidth tunability as well as a larger FSR It is well known and has been widely demonstrated that the high-order MRR can show a flat-top spectrum with welldesigned gap spacings [38,39,40,41,42]. We adjust the 3 dB bandwidth from 37.5 to 100 GHz with a step of 12.5 GHz, with the total IL varying from −5.4 to −7.9 dB and most of them showing flat-top responses
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