Fiber-based components

Transcription

1 Fiber-based components by: Khanh Kieu (02/26/2016)

2 Traditional optics Optical elements are used to split/combine, filter, focus, amplify, attenuate light Ti:sapphire laser

3 Fiber components Fiber splitter Beam splitter Fiber WDM Dichroic mirror Fiber Isolator Optical isolator

4 Fiber components Fiber coupler Variable fiber coupler WDM Isolator Attenuator Modulator Switches Pump/signal combiner Polarization splitter/combiner Collimator Fiber delay line Polarizer Tunable filter Circulator Faraday rotator mirror

5 Example of fiber devices Pump laser WDM Er-doped fiber Output Input Er-doped fiber amplifier Mode-locked ring fiber laser

6 (booster) amplifier transmission fiber dispersion compensation (in-line) amplifier transmission fiber dispersion compensation (pre-) amplifier WDM mux WDM demux EDFA EDFA EDFA Point-to-point WDM Transmission System - Building Blocks - l 1 l 2 transmitter terminal Tx transmission line point-to-point link section span amplifier span receiver terminal Rx l 1 l 2 l 3 SMF or NZDF SMF or NZDF l 3 l 4 DC DC l 4 l 5 l 5 l 6 l 6 l n Raman pump Raman pump l n

7 Fiber optic couplers Optical couplers either split optical signals into multiple paths or combine multiple signals onto one path The number of input (N)/ output (M) ports, (i.e. N x M ) characterizes a coupler Fused couplers can be made in any configuration, but they commonly use multiples of two (2 x 2, 4 x 4, 8 x 8, etc.)

8 Coupler applications Uses Splitter: (50:50) Taps: (90:10) or (95:05) Combiners Couplers are key components in Optical amplifiers Fiber lasers Optical switches Mach Zehnder interferometers Fiber-to-the-home networks Optical fiber sensors

9 Single-mode coupler properties Couplers are made by tapering fibers down, thereby making the core very small, resulting in most of the light propagating in the "multimode' cladding in the taper region If the adiabatic coupling regions vary slowly enough, then there is very little loss as the light propagates across the biconical taper

10 Fused biconic taper fabrication or Coupling ratio, excess loss, PDL Completely automated technology with high throughput

11 Coupler performance parameters (I) Coupling ratio or splitting ratio: CR = Power fromanysingleoutput Totalpower out toallports = P t P T-out æ P CR = -10log 2 ö 10 ç è P 1 + P 2 ø 2 x 2 case in db Excess loss: L e = P in P T-out æ P Le =10log in 10 ç è P 1 + P 2 ö ø 2 x 2 case in db

12 Coupler performance parameters (II) Insertion loss: L i = Power from any single output Power input Isolation or crosstalk: = P t P in æ L i = -10log 10 ç è In db P t P in ö ø Liso = Input power atoneport Reflected power back intoother input port æ L iso =10log 10 ç è P in P 3 ö ø In db

13 Fiber star coupler Combines power from N inputs and divided them between N outputs 1 P 1 1 N P N N Coupling ratio æ 1 CR = -10log 10 ç è N ö =10log 10 N ø Excess loss æ Le =10log ç 10 ç è å P in N P out,i i ö ø

14 Wavelength-dependent couplers Wavelength-division multiplexers (WDM) types: 3 port devices (4th port terminated) 1310 / 1550 nm ( classic WDM technology) 1480 / 1550 nm and 980 / 1550 nm for pumping optical amplifiers 1550 / 1625 nm for network monitoring Common l 1 l 2 Insertion and rejection: Low loss (< 1 db) for path wavelength High loss (20 to 50 db) for other wavelength

15 Wavelength-dependent couplers-wdm Fused biconic taper is made and monitored as it is being pulled When 1550nm is in the bar state and 1310nm is in the cross state, pulling is stopped - - a coarse WDM filter results

16 WDM couplers Fused coupler type WDM Low loss (<0.5dB) Small size (35x5.5mm) Low cost (~$200) Thin film type WDM

17 WDM couplers

18 Isolators Polarization sensitive isolator Polarization insensitive isolator Low loss (<0.5dB) Small size (35x5.5mm) Low cost (~$200)

19 Isolators

20 Project #6: Fiber-based components Goal: Learn the working principle of important fiber-based components (fiber splitter, WDM coupler, isolator, etc.) Characterize the performance of fiber-based components Tasks: Measure the splitting ratio and insertion loss of a fused fiber coupler Measure the wavelength response, insertion loss, and cross-talk of a 980/1550nm WDM coupler Measure the isolation and insertion loss of a fiber isolator

21 Questions for Thoughts What is the new fiber component that you think may be useful to have? Can we replace all traditional optics with fiber-based components? How can you turn your experimental setup into fiber-based? Where are fiber-based components made? How can you start a successful company providing fiber components and devices?