Fig. 1. Data synchronization and buffering in optical networks.

Fig. 2. Photonics-assisted microwave beam forming and steering in phased array radar systems.

Fig. 3. Microwave photonic delay-line filter with a finite impulse response. PD, photodetector; VOA, variable optical attenuator; MUX, multiplexer; DEMUX, demultiplexer.

Fig. 4. Typical system configuration of optical coherence tomography.

Fig. 5. Four-channel pulse interleaver using WDM-TDM implemented on a silicon chip^[27].

Fig. 6. Three types of cascaded ring resonator delay lines: (a) SCISSOR; (b) CROW in transmission mode; (c) CROW in reflection mode.

Fig. 7. Four types of integrated BGs with periodic modulation of (a) waveguide height, (b) waveguide width, (c) slab width, and (d) cladding.

Fig. 8. (a) Standard grating waveguide and its delay spectrum. (b) Cascaded complementary apodized gratings^[74].

Fig. 9. BG delay line based on a 60-nm-thick silicon waveguide^[35].

Fig. 10. ODLs based on (a) chirped BG^[73] and (b) linearly chirped contra-directional couplers with uniform BG^[80].

Fig. 11. ODL based on (a) line-defect PhCW and (b) coupled-cavity PhCW.

Fig. 12. Schematics of the switchable ODLs in (a) parallel and (b) serial configurations.

Fig. 13. 1×N optical switches based on (a) cascaded 1×2 switch elements and (b) optical phased array.

Fig. 14. (a) Architecture of the continuously tunable ODL structure; (b) mask layout of the ODL chip^[110].

Fig. 15. Recirculating loop delay line. (a) Integrated buffer; (b) gate matrix switch^[113].

Fig. 16. Recirculating loop delay line in a parallel switchable configuration.

Fig. 17. AWG-based wavelength-selective true-time-delay line. (a) Working principle illustration; (b) AWG layout.

Fig. 18. Implementation of an ODL based on frequency-to-time mapping.