研究目的
Investigating the suppression of undesired harmonics in opto-electronic oscillators using a combination of two slightly detuned bandpass microstrip filters.
研究成果
The study demonstrates an 8.3 dB improvement in the side-mode suppression ratio (SMSR) of a single-loop opto-electronic oscillator at 10.4 GHz by using a cascaded microstrip bandpass filter configuration. This approach does not increase the complexity of the OEO setup and offers a straightforward solution for enhancing the quality of the oscillator loop. Future research directions include exploring short, single-loop OEO configurations towards integrated solutions.
研究不足
The main limitation is the significant increase in insertion loss (IL) due to the cascaded connection of the filters, which necessitates the addition of an extra electrical amplifier to maintain the oscillating signal power. This could potentially introduce additional noise or complexity to the system.
1：Experimental Design and Method Selection:
The study involves designing a cascaded microstrip bandpass filter configuration to suppress side modes in a single-loop opto-electronic oscillator (OEO). The theoretical basis involves the multiplicative effect of cascading two filters to achieve increased attenuation at frequencies outside the region of overlap.
2：Sample Selection and Data Sources:
The OEO setup includes a 90-meter-long optical fiber delay line, electrical amplifiers, and the proposed cascaded microstrip bandpass filters. The filters are fabricated using a chemical etching process on a Rogers RO4350B substrate.
3：List of Experimental Equipment and Materials:
Key components include a Mach Zehnder Modulator (MZM), distributed-feedback (DFB) laser, electrical amplifiers, phase shifter, and the cascaded microstrip bandpass filters. The filters are designed using Keysight’s Advanced Design System (ADS) software.
4：Experimental Procedures and Operational Workflow:
The experimental setup measures the side-mode suppression ratio (SMSR) of the OEO under two conditions: with individual bandpass filters and with the cascaded filter network. An extra electrical amplifier is added to compensate for the increased insertion loss from the cascaded connection.
5：Data Analysis Methods:
The performance improvement is quantified by comparing the SMSR measurements obtained with a signal source analyzer (SSA) for both filter configurations.
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