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FBG and Applications. The F ilter that B reaks G rading Broptics Communications Corp. Fiber Grating.
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FBG and Applications The Filter that Breaks Grading Broptics Communications Corp.
Fiber Grating • Fiber grating is made by periodically changing the refraction index in the glass core of the fiber. The refraction changes are made by exposing the fiber to the UV-light with a fixed pattern. Glass core Glass cladding Periodic refraction index change (Gratings) Plastic jacket
trans. in reflect Reflection spectrum Transmission spectrum Fiber Grating Basics • When the grating period is half of the input light wavelength, this wavelength signal will be reflected coherently to make a large reflection. • The Bragg Condition n (refraction index difference) r = 2neff
Creating Gratings on Fiber • One common way to make gratings on fiber is using Phase Mask for UV-light to expose on the fiber core.
Characteristics of FBG • It is a reflective type filter • Not like to other types of filters, the demanded wavelength is reflected instead of transmitted • It is very stable after annealing • The gratings are permanent on the fiber after proper annealing process • The reflective spectrum is very stable over the time • It is transparent to through wavelength signals • The gratings are in fiber and do not degrade the through traffic wavelengths, very low loss • It is an in-fiber component and easily integrates to other optical devices
Temperature Impact on FBG • The fiber gratings is generally sensitive to temperature change (10pm/°C) mainly due to thermo-optic effect of glass. • Athermal packaging technique has to be used to compensate the temperature drift
Typical FBG Production Procedures Select Proper fiber H2 loading Laser writing Annealing Athermal packaging Testing
Current Applications of FBG • FBG for DWDM • FBG for OADM • FBG as EDFA Pump laser stabilizer • FBG as Optical amplifier gain flattening filter • FBG as Laser diode wavelength lock filter • FBG as Tunable filter • FBG for Remote monitoring • FBG as Sensor • ….
Possible Use of FBG in System ITU FBG filter Pump stabilizer & Gain flattening filter Wave locker Dispersion compensation filter E/O EDFA Multiplexer OADM Demux EDFA Switch ITU FBG filter Tunable filter Pump stabilizer & Gain flattening filter Monitor sensor ITU FBG filter Monitor
Circulator Circulator Circulator Circulator Circulator Circulator FBG at l1 FBG at l1 FBG at l2 FBG at l2 FBG at l3 FBG at l3 l1, l2 … ln l1, l2 … ln ... ... l1 l1 l2 l2 l3 l3 ITU FBG Filter for DWDM Multiplexer De-multiplexer
Incoming signal Outgoing signal Through signal Dropped signal Added signal ITU FBG Filter for OADM Circulator Circulator FBG
Dispersion Compensation Filter circulator Dispersed pulse Chirped FBG
+ Fiber 980 Stabilizer - Focal lens Pump Laser Pump Laser Stabilizer 980 spectrum
Gain Flattening Filter Gain profile GFF profile Output
Broptics Roadmap 25G FBG 50G FBG 100G FBG Pump laser stabilizer Wavelength lock Tunable filter Gain flattening filter Raman Amp Filter Remote monitor sensor Dispersion compensation Ceramic athermal package Mechanical athermal package 2001 2002