Data Sheet
2.5 Gb/s Buried Het 4x100GHz Tunable Laser
with extended reach option
LC25T
This laser module employs the Bookham gain coupled
SLMQW buried heterostructure DFB laser chip, and has been
designed specifically for use in Wavelength Division Multiplexed
(WDM) 2.5 Gb/s long distance optical fibre 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 module is tunable by means of the internal thermo-electric
cooler over four adjacent 100 GHz ITU WDM channels with a
case temperature of 70°C, or over two adjacent 100 GHZ
channels with a case temperature of 85°C
The device is available with a number of power options and
wavelength schemes, which are customizable to individual
customer specification.
Features:
• 2.5 Gb/s Operation
• Tunable over four separate channels at 100 GHz
channel spacing
• +/-95pm wavelength stability over life
• Entire C band ITU wavelengths available
(1528 to 1563 nm)
• Narrow spectral line-width
• Hermetically sealed 14-pin butterfly package with
optical isolator
• Internal TEC with precision NTC thermistor
• Extended reach performance up to 360 km with low
dispersion penalty
• RoHS compliant
Applications:
• Cost effective metropolitan or long haul networks
• Stock inventory / Spares reduction
• Network protection
• Low-speed routing / Networks reconfiguration
1
Data Sheet
Parameters
Parameter
Threshold current (I
th
)
Slope efficiency
2 mW
3 mW
4 mW
High Power [1]
[2]
1.3
[3]
[4]
-20 dB
34
[5]
50
250
0.4
40
125
1200
100
∆T
= 64°C
8 to 50°C
[6]
-45
4.07
20.7
1000
2.4
0.09
+145
1527
0.04
0.06
0.08
0.143
Conditions
Min
Typ
10
Max
22
0.09
0.13
0.17
0.43
-10
1.8
1563
2
0.6
Unit
mA
mW/mA
mW/mA
mW/mA
mW/mA
dB
V
nm
dB
nm
dB
ps
µA
nA
k
mA
V
nm/°C
pm
RF input reflection coef (S
11
)
Forward voltage
Peak wavelength (λ
p
)
Dispersion penalty
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
with laser temp.
∆T
= 64°C
Change of
λ
over life and
operating conditions
[1] The high power version provides 10 mW peak output power for 175 km applications and 7 mW peak ouput power for
360 km applications.
[2] 50 measurement system, f = dc - 3 GHz.
[3] Submount temperature between 8°C & 50°C start of life to achieve required
λ
p
.
[4] Dispersion penalty is compliant to a link length of 175 km or 360 km using an extinction ratio of 10dB. Fibre dispersion
characteristics are derived from the following equation:
4
0
3
D
(
λ
)
=
where So =0.092 ps/(nm
2
km) and
λ
0
= 1302 nm.
[5] Measurements determined from 20 - 80% Pk - Pk
[6] For more information on wavelength control and drift over life refer to application 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
λ
(
λ −
)
ps
/(
nm
.
km
)
4
λ
2
Data Sheet
Absolute Maximum Ratings
Parameter
Case operating temperature (with 2 x 100 GHz tuning)
Case operating temperature (with 4 x 100 GHz tuning)
Laser submount operating temperature
Storage temperature
Laser current above I
th
Laser reverse voltage
Laser reverse current
Monitor diode bias
Heat Pump Current
Heatpump voltage
Fibre bend radius
30
Min
-20
-20
8
-40
Max
85
70
50
85
100
1.0
10
-10
1
2.4
Unit
°C
°C
°C
°C
mA
V
µA
V
A
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 is held within the range 8°C to 50°C by the internal thermoelectric cooler and the product is
deployed in equal quantities on each of the four channels with a mean forward current of 35 mA. End of life limits based on 10 mA
increase in Ith and 25% change in laser efficiency. FIT rate data for other end of life criteria, including minimum extinction ratio
requirements, are available on request.
Outline Drawing
Figure 1: Outline Drawing and Pinout Information.
Note:
Device can be supplied with the leads trimmed to a length of 3.81 mm typ.
Please see Order Information section.
3
Data Sheet
Figure 2: Schematic Diagram.
Connections
Pin #
1
2
3
4
5
6
7
Function
Thermistor
Thermistor
Laser DC bias (-)
Monitor anode (-)
Monitor cathode (+)
TEC (+)
TEC (-)
Pin #
8
9
10
11
12
13
14
Function
Case ground
Case ground
N/C
Laser case ground
Laser modulation (-)
Laser case ground
N/C
Instructions for use – LC25T
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 100 µA to prevent
self-heating errors.
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 4 Monitor anode, Pin 5 Monitor cathode
The back facet monitor provides a mean power reference for the laser and is normally operated with a
5 V reverse bias.
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 2.4 V.
Pin 8, 9, 11, 13 Case ground
These pins must be grounded in all applications.
Pin 10
This pin is not connected for the LC25T product and it should be grounded if possible.
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.
4
Pin 14 N/C
This pin is not connected. It should be grounded if possible.
Data Sheet
Ordering Information
LC25T [Wavelength]
****
[Power Option]
E = 2 mWpk
C = 3 mWpk
A = 4 mWpk
B = High power
[Reach]
A = 175 km -
B = 360 km -
[Connector]
J28 = SC/PC
J34 = FC/PC
J57 = LC
J59 = MU
Fibre Length 1130 to 1190 mm.
Other connector types are available on request.
**** = Last four digits of first channel / shortest wavelength
E.g. LC25T4532CA-J28 has the following four channels:
1545.32
1546.12
1546.92
1547.72
nm
nm
nm
nm
The high power option provides 10 mW peak power at 175 km or 7 mW peak power over 360 km.
E.g.
LC25T4532BA-J28
is a 10 mW 1545.32 to 1547.72 nm device with an SC connector for use in a 175 km application.
E.g.
LC25T4532BB-J28
is a 7 mW 1545.32 to 1547.72 nm device with an SC connector for use in a 360 km application.
Trimmed lead option
Devices can be supplied with the leads trimmed to a length of 3.81 mm typ.
This option can be specified by adding a ‘K’ suffix after the reach option.
E.g.
LC25T4532BBK-J28
is a 7 mW 1545.32 nm device with an SC connector and a lead length of 3.81mm, for use in
a 360 km application.
-20°C to 85°C Case Temperature, 2 x 100 GHz Tunable Operation
Where a maximum case temperature of +85°C is required, the LC25T can be tuned over 2 adjacent 100 GHz channels.
With the elevated case temperature, the submount temperature tuning range becomes 25°C to 50°C.
Revised Parameters for 85°C Case Temperature Operation
Parameter
Thermistor resistance
Case operating temperature
Laser submount operating temperature
Conditions
Min
4.07
-20
25
Typ
Max
10
85
50
Unit
k
°C
°C
5
PCB Design
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