1 / 11

Optoelectronic Microwave Oscillators

Optoelectronic Microwave Oscillators. David Yoo Center for Microwave and Lightwave Engineering Drexel University ECE-E641 – Fiber Optics and Optical Communications I 2/20/03. Electronic Oscillators. First developed by L. De Forest in 1912

jillian-bauer
Download Presentation

Optoelectronic Microwave Oscillators

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Optoelectronic Microwave Oscillators David Yoo Center for Microwave and Lightwave Engineering Drexel University ECE-E641 – Fiber Optics and Optical Communications I 2/20/03 David Yoo

  2. Electronic Oscillators • First developed by L. De Forest in 1912 • Noise and stability limitations caused by ohmic and dispersive losses (e.g. in LC circuit) • But these limits can be overcome by combining oscillator with a high Q resonator David Yoo

  3. Loaded Quality Factor of Resonators • General Definition of Q, the Loaded Quality Factor of a Resonator David Yoo

  4. Optoelectronic Oscillators • Convert continuous light energy from a laser to RF and microwave signals • Use of fiber as an energy storage device results in signals with extremely low phase noise • Phase noise practically independent of absolute oscillation frequency David Yoo

  5. OEO Block Diagram Electro-Optic Modulator Optical Fiber Spool Optical Line Stretcher Laser Photodetector Microwave Output RF Coupler RF Bandpass Filter RF Amplifier Microwave Spectrum Analyzer David Yoo

  6. Conditions for Oscillation • Oscillation begins from noise • In order to have self-sustained oscillation : • Open loop gain of system must be greater than unity • An integer number of half-wavelengths must be in the loop David Yoo

  7. Loop Length and Frequency of Oscillation • The OEO loop can produce a comb of frequencies that satisfy the conditions for oscillation • The Free Spectral Range determines the distance between these frequencies • FSR in loop • Co is speed of light in vacuum • n is index of refraction • Lfiber is physical length of loop David Yoo

  8. Phase Noise of OEOs • Significant noises in an OEO (Yao & Maleki, 1996) • Thermal noise • Shot noise • Intensity noise of laser (RIN) • For high laser optical power, the phase noise of an OEO is limited by the laser’s relative intensity noise • For low laser power, thermal noise tends to dominate • Phase noises as low as -143 dBc/Hz at 10 kHz offset have been achieved for a 10 GHz carrier David Yoo

  9. OEWaves TIDALWave • Fixed frequency (up to 40 GHz) • -143 dBc/Hz @ 10 kHz offset • 10 dBm minimum output • 10” x 10” x 4” David Yoo

  10. Recent and Current Work on OEOs • Development of Compact OEOs (1999) • Use of semiconductor lasers and external modulators • Multiloop OEOs (2000) • The 2 fiber loops essentially act as the short and long cavities in a laser to select a single operation mode, and they also permit tunability • Miniaturization of OEOs (currently ongoing) • Replace fiber delay length with fused silica microspherical resonator • Such resonators have Q’s of 107-1010 for optical frequencies • Self Mode-Locking OEO (2002) David Yoo

  11. Important Points to Remember • Optoelectronic oscillators convert light energy from a laser into RF and microwave signals. • The fiber delays in OEOs are high Q because of the extremely low attenuation rate of fiber. • The phase noise of OEOs tends to be limited by the relative intensity noise of the system’s laser. David Yoo

More Related