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Seed account
"Microwave photonics" covers using optical components to generate, distribute, process or measure microwave and millimeter-wave signals. It is a broader field than RF-over-Fiber transport.
Main application areas
1. Signal transport: carrying RF over fiber between antennas and central equipment. Fiber has low loss per kilometre compared with coaxial cable, is immune to electromagnetic interference and is light. Used in distributed antenna systems, antenna remoting for satellite ground stations and radio astronomy, and some radar systems.
2. Signal generation: beating two lasers on a fast photodiode produces an RF tone at their frequency difference. With phase-locked lasers or optical frequency combs, very high frequencies can be generated. Optoelectronic oscillators (OEOs) use a long fiber delay as a high-Q element and can achieve low phase noise at high carrier frequencies.
3. Signal processing: photonic filters, true-time-delay beamforming for phased arrays (delay rather than phase shift avoids beam squint over wide bandwidths), and photonic analog-to-digital conversion using low-jitter mode-locked lasers.
4. Timing and frequency distribution: stabilized fiber links distribute reference frequencies and timing signals over long distances with very low added noise, used in large science facilities.
Key components
- Lasers (DFB, external cavity, mode-locked), modulators (MZM, electro-absorption, phase), photodiodes (PIN, uni-travelling carrier for high power), optical amplifiers (EDFA), fiber and passive optics.
Key performance metrics are the same ones RF engineers already know: gain, noise figure, linearity (P1dB, IP3, SFDR), bandwidth and phase noise. The difference is that they are set by optical power, modulation efficiency and detector characteristics.
Suggested starting point: the review literature on microwave photonics in IEEE and Optica journals, then a careful read of a few RFoF datasheets to connect theory with practice.
Main application areas
1. Signal transport: carrying RF over fiber between antennas and central equipment. Fiber has low loss per kilometre compared with coaxial cable, is immune to electromagnetic interference and is light. Used in distributed antenna systems, antenna remoting for satellite ground stations and radio astronomy, and some radar systems.
2. Signal generation: beating two lasers on a fast photodiode produces an RF tone at their frequency difference. With phase-locked lasers or optical frequency combs, very high frequencies can be generated. Optoelectronic oscillators (OEOs) use a long fiber delay as a high-Q element and can achieve low phase noise at high carrier frequencies.
3. Signal processing: photonic filters, true-time-delay beamforming for phased arrays (delay rather than phase shift avoids beam squint over wide bandwidths), and photonic analog-to-digital conversion using low-jitter mode-locked lasers.
4. Timing and frequency distribution: stabilized fiber links distribute reference frequencies and timing signals over long distances with very low added noise, used in large science facilities.
Key components
- Lasers (DFB, external cavity, mode-locked), modulators (MZM, electro-absorption, phase), photodiodes (PIN, uni-travelling carrier for high power), optical amplifiers (EDFA), fiber and passive optics.
Key performance metrics are the same ones RF engineers already know: gain, noise figure, linearity (P1dB, IP3, SFDR), bandwidth and phase noise. The difference is that they are set by optical power, modulation efficiency and detector characteristics.
Suggested starting point: the review literature on microwave photonics in IEEE and Optica journals, then a careful read of a few RFoF datasheets to connect theory with practice.