1 / 35

Optical Components

Optical Components. Ajmal Muhammad, Robert Forchheimer Information Coding Group ISY Department. Outline. Types of optical components Passive (reciprocal & non-reciprocal ) Lens, couplers, isolators, circulators, filters, multiplexer, demultiplexer Active

lilia
Download Presentation

Optical Components

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. Optical Components Ajmal Muhammad, Robert Forchheimer Information Coding Group ISY Department

  2. Outline • Types of optical components • Passive (reciprocal & non-reciprocal) Lens, couplers, isolators, circulators, filters, multiplexer, demultiplexer • Active Modulator, switch, optical amplifier, wavelength converter, gain equalizer • Wavelength Selectivity • Fixed • Tunable • Parameters Temperature dependency, insertion loss (inputoutput loss) inter-channel cross-talks, fast tunability, stability and polarization dependency

  3. Requirements • Bandwidth • Low insertion loss (inputoutput loss) • High return loss (outputinput loss) • Polarization insensitivity • Low crosstalk • High extinction ratio • Temperature insensitivity • Low control power • Small size • Cost

  4. Optical Component Platform • Micro-optic components The assembly of discrete elements are placed together in an optical component. The elements require precise optical alignment to maximize the performance. • Integrated optics components Uses planar manufacturing techniques to develop devices such as Array Waveguide Grating (AWG), Variable Optical Attenuators (VOA), Electro-optic Modulators, etc. • Fiber based optical components Devices made of fibers such as fusedoptical couplers, fused WDMs, Fiber-Bragg gratings (FBG), etc. • Hybrid type

  5. Passive Components • Coupler: versatile device used as a building block for several other optical devices • Isolator: used in systems at the output of amplifiers and lasers to prevent reflections • Filter: to multiplex and demultiplex wavelengths in a WDM system, and to provide equalization of the gain and filtering of noise in optical amplifier • MUX & DEMUX: MUX combines signals at different wavelengths on its input ports onto a common output port, DEMUX performs the opposite function

  6. Couplers Couplers • Structure • NxN (e.g., 2x2) • α is proportional to l (α is coupling ratio, l is coupling length) • Parameters of interest • Coupling ratio • Coupling length • Excess loss (beyond α) • Type • Wavelength dependent (α has wavelength-dependency) • Wavelength independent (wavelength flat) • Splitting ratio • 3dB (splitting the power evenly) - α=0.5 • Taps (e.g., α ∼ 1 – thus, a very small portion is dropped)

  7. Couplers - Passive Reciprocal Device • They can combine or separate different wavelengths • The lights (different wavelengths) are coupled together • Example: 8x8 3-dB couplers 1310 (signal) Amplified Signal 1550 nm (pump) Wavelength-dependent coupler Multiple signals combined and broadcast to many outputs

  8. Couplers 1x2 coupler 6x6 coupler

  9. Isolators - Passive Non-Reciprocal Device • Transmit in one direction only • Avoid reflection of laser – or any reflection • One input, one output or multiple ports • Key parameters are insertion loss and excess loss • Example: circulator

  10. Operation of Isolators

  11. Isolators

  12. Passive Components • Coupler: versatile device used as a building block for several other optical devices • Isolator: used in systems at the output of amplifiers and lasers to prevent reflections • Filter: Variety of technologies are available

  13. Gratings Describe a device involving interference among multiple optical signals coming from the same source but having difference phase shift There are a number of gratings • Reflective • Transmission • Diffraction • Stimax (same as reflection but integrate with concave mirrors)

  14. Gratings • Transmission gratings • The incident light is transmitted through the slits • Due to diffraction (narrow slits) the light is transmitted in all direction • Each slit becomes a secondary source of light • A constructive interference will be created on the image plane only for specific WLs that are in phase  high light intensity • Narrow slits are placed next to each other • The spacing determines the pitch of the gratings • Angles are due to phase shift Transmission gratings Reflective gratings Diffraction gratings

  15. Fiber Bragg Gratings Any periodic perturbation in the propagation medium serves as a Bragg gratings Diffractive optical element

  16. Optical Add/Drop Using Fiber Bragg Grating

  17. Fabry-Perot Filters A cavity with highly reflective mirrors parallel to each other (Bragg structure) • Acts like a resonator • Also called FP Interferometer • Used in lasers

  18. Tunability of Fabry-Perot • Changing the cavity length (l) • Varying the refractive index (n) within the cavity • Mechanical placement of mirrors Not very reliable • Using piezoelectric material within the cavity Thermal instability

  19. Multilayer Dielectric Thin Film Filters • Dielectric thin-film (DTF) interference filters consist of alternating quarter-wavelength thick layers of high refractive index and low refractive index each layer is a quarter-wavelength thick. • The primary considerations in DTF design are: • Low-pass-band loss (« 0.3 dB) • Good channel spacing (> 10 nm) • Low inter-channel cross-talk (> -28 dB) DTF filters MUX/DEMUX using DTF filters

  20. Mach-ZehnderInterferometer • Uses two couplers • The coupling ratio can be different • A phase difference between two optical paths may be artificially induced • Adjusting ΔL changes the phase of the received signal • Because of the path difference, the two waves arrive at coupler 2 with a phase difference • At coupler 2, the two waves recombine and are directed to two output ports • each output port supports the one of the two wavelengths that satisfies a certain phase condition • Note: • Δf=C/2nΔL • ΔΦ=2πf.ΔL.(n/c)

  21. Tunability Can be achieved by altering n or L

  22. Arrayed Waveguide Grating (AWG) AWG is a generalization of the Mach-Zehnder interferometer

  23. AWG as DEMUX and Cross-Connect Input coupler Arrayed guides Output coupler Static Wavelength Cross-connect

  24. Multiplexer/Demultiplexer

  25. Multiplexer/Demultiplexer

  26. Active Components • Modulator, switch, and router • Optical amplifier (fiber amplifier, semiconductor amplifier) • Wavelength converter • Gain equalizer Optical switch can be used for:1) Light modulation(phase & intensity)2) Routing optical data

  27. Type of Optical Modulators/Switches

  28. Micro-Electro-Mechanical (MEMS) Switch

  29. Electro-Optic Modulator Need material with high electro-optic effectElectro-optic: refractive index change is proportional to applied electric field

  30. Wavelength Converter

  31. Different types of Wavelength Converter • OE/EO regeneration • SOA-based Cross-gain modulation Cross-phase modulation Four-Wave mixing • Fiber-based Cross-phase modulation Four-Wave mixing OE/EO Cross-gain Cross-phase Four-Wave mixing

  32. Gain Equalizers

  33. Gain/Power Equalizers

  34. Gain/Power Equalizers

More Related