1. Lecture Note on Optical Components

2. Optical Couplers Combines & splits signals Light couples from one waveguide to a closely placed waveguide because the propagation mode overlaps the two waveguides Wavelength independent or selective Fabricated using waveguides in integrated optics  = coupling ratio Power (Output1) =  Power (Input1) Power (Output2) = (1-  ) Power (Input1) – Power splitter if  =1/2: 3-dB coupler – Tap if  close to 1 – -selective if  depends upon Lossless combining is not possible

3. 8-Port Splitter by Cascading Y-Couplers

4. 8x8 Star Coupler Power from all inputs equally split among outputs

5. Isolators and Circulators Extension of coupler concept Non-reciprocal type will not work same way if inputs and outputs reversed Isolator allows transmission in one direction, but blocks all transmission (e.g., reflection) in the other. Circulator is similar to isolator, but with multiple ports.

6. Filters and Multiplexers

7. Low insertion (input-to-output) loss Filter passband independent of temperature Flat passband Sharp skirts on the passband & crosstalk rejection Filters

8. Device using interference among optical signals from same source, but with different relative phase shifts (i.e. different path lengths) Gratings

9. Transmission versus Reflection Grating

10. Diffraction Gratings

11. Mux/Demux Using Cascaded Filters Each filter passes one and reflects the other s Very flat top and sharp skirts

12. Amplification

13. Optical Amplifiers versus Regenerators 40-80 km Terminal Regenerator - 3R (Reamplify, Reshape and Retime) Terminal 120 km Terminal EDFA - 1R (Reamplify) Terminal EDFA amplifies all s Terminal EDFA is a common optical amplifier.

14. OEO Regenerator

15. 1R, 2R and 3R Regenerations 1R = Reamplify 2R = Reamplify, Reshape 3R = Reamplify, Reshape, Retime

16. Regenerators versus Optical Amplifiers Regenerators specific to bit rate and modulation format used; optical amplifiers are insensitive. A system with optical amplifiers can be more easily upgraded to higher bit rate without replacing the amplifiers. Optical amplifiers have large gain bandwidths => key enabler of DWDM Issues –Amplifiers introduce additional noise that accumulates. –Spectral shape of gain (flatness), output power, transient behavior need to be carefully designed.

17. Optical Regenerator

18. Optical Receivers

19. Electronic versus Photonic Coding

20. Optical Modulation Methods

21. Eye Diagrams

22. WDM Multiplexing TDM: 10Gb/s upper limit WDM: Use multiple carrier frequencies to transmit data simultaneously... B b/s NB b/s 12N12N 12N12N B b/s

23. Filter selects one wavelength and rejects all others Multiplexer combines different wavelengths Router exchanges wavelengths from one input to a different output Multiplexers, Filters, Routers

24. Considerations in Switch Number of switch elements: complexity of switch Loss uniformity: different losses to different outputs (especially for large switches) Number of crossovers: waveguide crossovers introduce power loss and crosstalk Blocking: any unused input port can be connected to any unused output port

25. Crossbar Switch Non-blocking Shortest path length = 1 Longest path length = 2n-1 No crossover

26. Clos Switch

27. Benes Switch

28. MEMS Mirror Switching Component

29. NxN Switching with MEMS Mirror Arrays