An Optoelectronic Equivalent Narrowband Filter for High Resolution Optical Spectrum Analysis

Area of Science:

• Optoelectronics
• Optical Engineering
• Spectroscopy

Background:

• Advanced optical spectrum analysis (OSA) requires narrow bandwidth filters with wide swept ranges.
• Existing filters face limitations in achieving both narrow bandwidth and broad sweep capabilities for high-performance optical sensors.

Purpose of the Study:

• To investigate and develop an optoelectronic equivalent narrowband filter (OENF) for next-generation OSA.
• To achieve a filter with a bandwidth of several MHz and a sweep range of several tens of nanometers.
• To enhance the analysis of fine spectral structures in optical sensor data.

Main Methods:

• Designed and built a swept optical filter using electric filters and a sweep laser as a local oscillator (LO).
• Optimized two electric filters as resolution bandwidth (RBW) filters for high and medium spectral resolution.
• Implemented a real-time wavelength calibration system using a HCN gas cell and Fabry-Pérot etalon.

Main Results:

• Verified the OENF principle through simulations and experiments, showing power uncertainty <1.2% and spectral resolution up to 6 MHz.
• Achieved wavelength accuracy of ±0.4 pm in the C-band, mitigating LO sweep phase noise and nonlinear velocity effects.
• Demonstrated the OENF system's capacity for analyzing fine spectrum structures in OSA experiments on various optical sensors.

Conclusions:

• The developed OENF system effectively meets the demands for narrow bandwidth optical filtering with a wide swept range.
• The system provides high spectral resolution and accuracy, crucial for advanced optical spectrum analysis.
• OENF technology offers a promising solution for analyzing complex spectra from high-performance optical sensors.