Abstract
Precise optical spectrum analysis with high resolution by an economical and reliable device is of much interest in optical science and technology. In this work, we propose a silicon-photonic integrated optical spectrum analyzer comprised of two cascaded filters. A first ring resonator stage selects multiple ultra-narrow spectral bands of equal spacing. The set of bands may be scanned across the spectrum of interest through thermal tuning. A second filter stage separates the multiple sampled bands into different output ports. The free spectral ranges of the two stages are matched. The spectrum is reconstructed using simple, low bandwidth photodiodes. In a proof of concept experiment, the proposed integrated optical spectrum analyzer shows a wide operational range with 128MHz resolution.
Highlights
H IGH-PRECISION analysis of the power spectral density is among the most fundamental measurement protocols
The proper function of wavelength division multiplexed (WDM) networks critically depends on tight spectral control and careful monitoring of signal-to-noise ratios, sidemode suppression and more [2]
WDM devices are readily implemented in silicon as well [15], [22]–[27], in the forms of arrayed waveguide gratings (AWGs) [15], [23], cascaded MachZehnder interferometers (MZIs) [25], and more complex layout that combine MZIs and resonators [27]
Summary
H IGH-PRECISION analysis of the power spectral density is among the most fundamental measurement protocols. State of the art commercial instruments reach around 2 GHz resolution at telecommunication wavelengths, high-resolution grating spectrometers are often expensive, bulky, and complex because of the inverse relationship between spectral resolution and free-space optical path length. They are sensitive to environmental shocks and vibrations, which limit their application areas. Thereby, the narrow Brillouin gain is shifted through the unknown spectrum, amplifies the signal under test and the power is recorded versus the wavelength These systems show a resolution of 10 MHz, which can be decreased down to 3.4 MHz [8], [9]. In a proof of concept experiment, the optical power spectrum of a 20 Gbps pseudo-random bit sequence (PRBS) signal, is characterized over 50 GHz bandwidth with a spectral resolution of 128 MHz (∼ 1 pm)
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