DWDM 1.25 Gb/s DFB Laser Module
with Integral Optical Isolator
Technical Data
LSC26xx
Features
• Center Wavelength between
1528 nm and 1602 nm
• Extended Wavelengths for
use in systems requiring no
amplifiers
• Modulation Capability up
to 1.25 Gb/s
• 30 dB Internal Optical
Isolation
• 25
W
Impedance Matched
• Wide Operating Temperature
Range: -20°C to +70°C
• Industry Standard Hermetic
14 PIN Butterfly Package
Description
LSC26xx laser modules are highly
reliable fiber optic light sources
operating in the 1550 nm band.
The internal DFB lasers are
based upon InGaAsP ridge
waveguide Multi Quantum Well
technology and fabricated by the
Metal Organic Vapor Phase
Epitaxy (MOVPE) process,
resulting in long lifetimes and
modest threshold currents.
The LSC26xx package includes a
photodiode for monitoring the
laser output, a thermistor for
monitoring laser heatsink
temperature, and a Peltier effect
thermoelectric cooler (TEC). A
heatsink mounting flange is
incorporated into the industry
standard 14 PIN package, and the
TEC supports
∆T
of ±50°C.
The LSC26xx also has 30 dB of
optical isolation which is
temperature controlled to
maintain isolation over the full
operating temperature range.
The LSC26xx family of parts
gives full DWDM coverage in the
EDFA 1550 nm window and
offers extended wavelengths for
use in systems which do not
require amplifiers.
Applications
• Metropolitan DWDM
• SONET/SDH Systems
• ATM, Ethernet and
Proprietary
Datacommunication
Networks
• FTTC
Laser Safety Warning
This device is a Class IIIb (3b) Laser Product. It may emit invisible laser radiation if operated with the fiber pigtail disconnected.
To avoid possible eye damage do not look into an unconnected fiber pigtail during laser operation. Do not exceed specified operating limits.
2
Wavelength Control
Wavelength tuning is achieved by
adjusting the laser chip
temperature. The laser chip
temperature is monitored using
the internal thermistor. The
Peltier effect thermoelectric
cooler deployed in the LSC26xx
is capable of maintaining a ±50°C
temperature difference. The
heating mode occurs when pin 7
is positive with respect to pin 6
and the reverse is required for
cooling to happen.
R.F. Matching
For optimum high-speed
performance the r.f. matching of
the drive current is important in
directly modulated lasers. The
LSC26xx has an internal 25 ohm
matching circuit to allow ease of
use. There are several options for
providing laser DC bias to the
LSC26xx. The most widely
deployed option is dc biasing via
pin 3 and modulating via pin 12.
Alternatively, some laser driver
ICs allow both modulation and
biasing via their output pin (to
LSC26xx pin 12) which results in
pin 3 being unused. Under such a
biasing scheme, it is
recommended that pin 3 be
decoupled to ground via a 100 nF
capacitor to prevent any RF
injection or pickup. The latter
method is generally avoided due
to the additional heat dissipation
within the laser driver IC which
impacts overall performance.
3
LSC26xx Mechanical Outline
Top View
A
S
B
U
ØT
R
I
H
Back
View
C
F
J
Side View
L
K
D
G
V
E
M
Dim
A
B
C
D
E
F
G
H
I
J
K
L
M
N
P
R
S
T
U
V
Min
29.6
20.6
12.45
8.4
-
-
5.40
-
-
-
-
-
400
-
4.5
8.7
25.8
2.50
-
-
Nom
-
-
-
-
0.75
12.0
-
2.54
0.50
0.20
7.0
30.0
-
2.0
-
-
-
-
0.75
17.8
Max
30.4
21.1
12.95
9.0
-
-
5.90
-
-
-
-
-
-
-
6.5
9.1
26.2
2.70
-
-
All dimensions in mm
N
P
LSC26xx Pin Connections
and Block Diagram
Top View
7 6 5 4 3 2 1
TEC
8 9 10 11 12 13 14
Pin Connections
1
Thermistor
2
Thermistor
3
Laser dc bias
4
Monitor Anode
5
Monitor Cathode
6
TEC -ve when heating
7
TEC +ve when heating
8
Ground
9
Ground
10
Not connected
11
Ground
12
Laser modulation
13
Ground
14
Not connected
4
LSC26xx Typical Operating Characteristics
PRODUCT TYPE
MODULATION BIT RATE
MODULATION DEPTH
Thermistor res @ +25°C
Wavelength
Thermistor res on channel
Dark current
Threshold Current (Ith)
Power at Ith
Power at Ith + 40 mA
Slope efficiency
: LSC26xx
: 1.25 Gb/s
: 10% Extinction Ratio
kohm
nm
kohm
nA
mA
µW
µW
mW/mA
10.393
1547.73
10.980
0.48
16.00
0.00
2123.00
0.053
5
Absolute Maximum Ratings at +25°C
Absolute limiting (maximum) ratings mean that no catastrophic damage will occur if the product is subjected to these ratings for short periods,
provided that each limiting parameter is in isolation and all other parameters have values within the performance specification. It should not be
assumed that limiting values of more than one parameter can be applied to the product at the same time.
Parameter
Laser Forward Current
Laser Reverse Voltage
Photodiode Forward Current
Photodiode Reverse Voltage (Vr)
Fiber Pull Strength
Operating Temperature (Case)
Storage Temperature
Mechanical Shock
Vibration
TEC Current
TEC Voltage
Minimum
Maximum
-
150
-
3.3
-
2.5
-
-10
-
10
-20
+85
-40
+85
MIL-STD 883, Method 2002, Test Condition B
MIL-STD 883, Method 2007, Test Condition A
-
1.1
-
3.0
Units
mA
V
mA
V
N
°C
°C
A
V
Performance Specifications - Laser
Parameter
Threshold Current (Ith) [1]
Peak Wavelength [2] [3]
Spectral Width (-30 dB) Modulated [3]
Peak Wavelength Change with Chip Temperature [1]
Sidemodes suppression ratio (Modulated) [3]
Tracking Error, +75°C case, +25°C chip [4]
Tracking Error,
-20°C case, +25°C chip
Flatness of Frequency Response (300 MHz to 2 GHz)
Slope Efficiency [1]
Output Power (Peak Power, pk) [1]
Center Wavelength Drift with Case Temperature
Minimum
10
1528
-
-
34
-
-
-
0.05
2
-
Typical
-
-
-
0.08
-
-
-
-
-
-
0.2
Maximum
35
1602
0.6
0.2
-
0.5
0.5
±1.5
-
-
0.5
Units
mA
nm
nm
nm/°C
dB
dB
dB
dB
mW/mA
mW
pm/°C
Dispersion Penalty
[5]
Data Rate
1.25 Gb/s
622 Mb/s
Distance
[6]
120 km
400 km
Dispersion Penalty (maximum)
2 dB
2 dB
Notes
1. Laser chip temperature between +20°C and +30°C.
2
Exact peak wavelength is specified in the table on page 7.
3. At PRBS 2
23-1
, 1.25 Gb/s, Extinction Ratio = 10%, Mean Output Power >1 mW.
4. Fiber output power change for constant monitor output current.
5. At PRBS 2
23-1
, Extinction Ratio = 10%, Mean Output Power >1 mW.
6. Fiber dispersion 17 ps/nm/km.
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