Data Sheet
2.5Gb/s Buried Het Laser 175km Reach
With Optional Etalon Stabilization
LC25W-A (175km)
This laser module employs the Bookham strained layer
MQW Buried Heterostructure DFB laser chip, and has been
designed specifically for use in Wavelength Division
Multiplexed (WDM) 2.5Gb/s long distance optical fiber
trunk systems.
The device is packaged in a hermetically sealed 14-pin
butterfly package incorporating an isolator and monitor
photodiode for control of the power of the laser over life and
all operating conditions. The device is available with a number
of power options depending on application and link
span requirements.
The optional internal Etalon wavelength stabilization and low
chirp performance makes this product compliant with 50GHz
optical channel spacing.
Features:
• 2.5Gb/s operation
• +/-95pm wavelength stability over life without
Etalon locker
• Optional Etalon wavelength stabilization provides
50GHz optical channel spacing compliance for interlay
or future upgrade
• Narrow spectral line-width
• Internal TEC with precision NTC thermistor for
temperature control
• Entire C & L-band ITU wavelengths available
(1527nm to 1605nm)
• Code reduction with single product for reaches
up to 175km
• GaInAsP SLMQW DFB single frequency laser chip
• InGaAs monitor photo-diode
• Hermetically sealed 14-pin butterfly package with
optical isolator
• RoHS compliant
Applications:
• WDM
• On-off ramps
• Long-Haul
• DWDM on ITU Grid
1
Data Sheet
Parameters
Parameter
Threshold current (I
th
)
Slope efficiency by product
2 mW
3 mW
4 mW
10 mW
[1]
Conditions
Min
Typ
10
Max
22
0.09
0.13
0.17
0.43
-10
Unit
mA
mW/mA
0.04
0.06
0.08
0.143
RF input reflection coef (S
11
)
Forward voltage
Peak wavelength (λ
p
)
Dispersion penalty at 175 km
Time averaged spectral linewidth
Side-mode suppression
Optical rise/fall time
Monitor photo current
Monitor dark current
Thermistor resistance
Heatpump current
Heatpump voltage
Change of
λ
p
with laser temp.
Change in
λ
over life and
operating conditions
Optical Spectral Window
dB
V
nm
dB
nm
dB
1.3
[2]
[3]
1.8
1605
2
1527
-20 dB
32
[4]
0.1
40
0.6
125
50
40
250
250
1200
360
100
10
ps
µA
nA
k
Unlocked
Etalon locked
70°C case temperature
70°C case temperature
15°C to 35°C
Unlocked
[5]
250
600
1.0
0.09
900
2.4
mA
V
nm/°C
-45
-9
+145
+9
pm
GHz
Locked, over life & temperature
including chirp
[5]
[1] 50
measurement system, f = dc - 3GHz.
[2] Submount temperature between 20°C to 35°C start of life to achieve required
λ
p
. For the 10mW version, submount
temperature is between 15°C to 35°C start of life.
[3] Standard product dispersion penalty will be compliant to the specified link length of 175km using an extinction ratio of 10dB.
Fiber dispersion characteristics are derived from the following equation.
Where So = 0.092ps/(nm
2
.km) and
λ=
1302nm.
[4] Measurements determined from 20 - 80% pk - pk.
[5] For more information on wavelength control and drift over life refer to applications note DR1670. To give symmetrical
wavelength performance about the ITU channel wavelength (+/-95pm) offset the laser wavelength by –50pm at start of life
set up.
So
D
( )
=
(
-
4
4
0
3
)
ps
/(
nm
.
km
)
2
Data Sheet
Absolute Maximum Ratings
Parameter
Case operating temperature
Laser submount operating temperature
Storage temperature
Laser current above Ith
Laser reverse voltage
Laser reverse current
Monitor diode bias
Heatpump voltage
Fiber bend radius
Notes:
[1] Product without locker can be tuned onto the next 100GHz ITU channel in the red shift direction (2x100GHz tunability) by increasing the
submount temperature to a maximum of 43°C.
[2] For the 10mW version, the minimum laser submount operating temperature is 15°C.
[1] [2]
Min
0
20
-40
Max
70
35
85
100
1.0
10
-10
2.4
30
Unit
°C
°C
°C
mA
V
µA
V
V
mm
Reliability/Quality
Meets qualification requirements of Telcordia / Bellcore GR468-Core for central office environment.
Operating reliability <500 FITs
1
in 15 years.
1- Assumes laser die submount held at <35°C by internal thermoelectric cooler, mean forward current of 35
mA, and end of life limits based on 10 mA increase in I
th
and 25% change in laser efficiency. FIT rate data for
other end of life criteria, including minimum extinction ratio requirements, are available upon request.
Outline Drawing
Dimensions (mm)
Figure 1: Outline Drawing
Note:
3
Devices can be supplied with the leads trimmed to a length of 3.81 mm. Please see Ordering Information section.
Fiber length: 1130mm to 1190mm
Data Sheet
Instructions for use – LC25W****A/LC25EW****A
Pin 1 and Pin 2 Thermistor
The thermistor is used in a control loop in conjunction with
the thermo-electric cooler to maintain the laser submount
temperature at the required value for wavelength.
Operating current should be less than 100µA to prevent
self-heating errors.
For Etalon stabilized devices the thermistor is used for the
initial set up of the submount temperature at the required
wavelength value. Operating current should be less than
100µA to prevent self-heating errors. Once the initial
submount temperature has been achieved control of the TEC
current is handed over to the Etalon locking circuit to achieve
fine tuning.
Pin 8, 9, 11, 13 Case ground
These pins must be grounded in all applications.
Pin 10
This pin is not connected for the LC25W product and it
should be grounded if possible. For the Etalon locked
product this pin is used for the monitor long anode.
The monitor diodes are arranged such that they give an
equal monitor current when the laser wavelength is matched
to the ITU grid. A reverse bias must be applied equally across
each of the monitors, this is commonly achieved by applying
5V to pin 5.
Pin 3 Laser DC bias (-)
Laser bias current (negative with respect to package ground)
is applied via this pin which forms one side of the bias-T
connection to the laser cathode.
Pin 12 Laser modulation (-)
The data input (modulation current) is applied via this pin
which is a nominal 25 Ohm impedance coplanar line.
For 10mW applications the end of life modulation current is
90mA maximum. For all other applications 60mA maximum
modulation current should be provisioned.
Pin 4 Monitor anodes, Pin 5 Common Monitor cathode
The back facet monitor provides a mean power reference for
the laser and is normally operated with a 5V reverse bias.
For Etalon stabilized devices the monitor diodes are arranged
in the package such that they give an equal monitor current
when the laser wavelength is matched to the ITU grid. A
reverse bias must be applied equally across each of the
monitors, this is commonly achieved by applying 5V to Pin 5.
Pin 14 N/C
This pin is not connected. It should be grounded if possible.
Pin 6 TEC (+), Pin 7 TEC (-)
Applying a positive voltage on pin 6 with respect to pin 7 will
cause the internal submount to be cooled relative to the case
temperature. Reversing the polarity will raise the submount
temperature relative to the case. The TEC supply should be
capable of delivering up to 0.9 A at 2.4V.
4
Data Sheet
Connections
Without Etalon
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Function
Thermistor
Thermistor
Laser DC bias (-)
Monitor Anode (-)
Monitor Cathode (+)
TEC (+)
TEC (-)
Case Ground
Case Ground
Not Connected
Case Ground
Laser Modulation (-)
Case Ground
Not Connected
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
With Etalon
Function
Thermistor
Thermistor
Laser DC bias (-)
Monitor Short Anode (-)
Monitor Cathode (+)
TEC (+)
TEC (-)
Case Ground
Case Ground
Monitor Long Anode (-)
Case Ground
Laser Modulation (-)
Case Ground
Not Connected
Safety Information
Laser safety classifications:
IEC 60825-1: Edition 1.2 Class 1M
21 CFR Ch.1 (4-1-97 Edition) Class IIIb
Electrostatic discharge:
ESD threshold >500V
TA-TSY-000870 class 3.
5
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