Transcript FBG and Applications - Welcome to Broptics

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
Plastic jacket
Periodic refraction index change
(Gratings)
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
trans.
in
reflect
Reflection spectrum

Transmission spectrum
n
r = 2neff 
(refraction index difference)
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
1535.2
1535.0
1534.8
Center Wavelength (nm)

1534.6
1534.4
1534.2
Athermal
1534.0
Normal
1533.8
-5
15
35
Temperature (℃ )
55
75
Types of Fiber Gratings
TYPES
CHARACTERS
APPLICATIONS
Simple reflective
gratings
Creates gratings on the fiber that
meets the Bragg condition
Filter for DWDM,
stabilizer, locker
Long period
gratings
Significant wider grating periods
that couples the light to cladding
Gain flattening filter,
dispersion
compensation
Chirped fiber
Bragg gratings
A sequence of variant period
gratings on the fiber that reflects
multiple wavelengths
Gain flattening filter,
dispersion
compensation
Slanted fiber
gratings
The gratings are created with an
angle to the transmission axis
Gain flattening filter
Typical FBG Production Procedures
Select
Proper
fiber
H2
loading
Different
FBG
requires
different
specialty
fiber
Increase
photo
sensitivity
for easier
laser
writing
Laser
writing
Optical
alignment &
appropriate
laser writing
condition
Annealing
Enhance
grating
stability
Athermal
packaging
For
temperature
variation
compensation
Testing
Spec test
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
Wave locker
ITU FBG filter
E/O
Multiplexer
Demux
ITU FBG filter
Pump stabilizer &
Gain flattening filter
Dispersion
compensation filter
Dispersion
control
EDFA
OADM
EDFA
Switch
Pump stabilizer &
Gain flattening filter
ITU FBG filter
Tunable filter
Monitor sensor
Monitor
ITU FBG Filter for DWDM
Circulator
 1,  2 …  n
Multiplexer
FBG at 1
1
Circulator
 1,  2 …  n
1
De-multiplexer
FBG at 1
Circulator
FBG at 2
Circulator
2
3
Circulator
Circulator
2
FBG at 2
3
FBG at 3
FBG at 3
...
...
ITU FBG Filter for OADM
Incoming signal
Outgoing signal
Through signal
Circulator
Circulator
FBG
Dropped signal
Added signal
Dispersion Compensation Filter
circulator
Dispersed
pulse
Chirped FBG
Pump Laser Stabilizer
+
Fiber
Pump Laser
Focal lens
980
spectrum
980 Stabilizer
Gain (dB)
Gain Flattening Filter
20
Gain profile
15
GFF profile
10
Output
5
0
-5
-10
-15
1500
1520
1540
1560
Wavelength (nm)
1580
1600
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