Data Sheet
2.5 Gb/s Buried Het 4x100GHz Tunable Laser with
Etalon Stabilisation and extended reach option
LC25ET
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 locking optics
to lock and stabilise wavelength and power of the laser
over life.
The module is tunable by means of the internal thermo-electric
cooler over four adjacent 100 GHz ITU WDM channels.
The device is available with a number of power options and
wavelength schemes, which are customizable to individual
customer specification. The internal etalon wavelength
stablilisation and low chirp performance makes this product
compliant with 50GHz optical channel spacing.
Features:
• 2.5 Gb/s Operation
• Tunable over four separate channels at 100 GHz
channel spacing
• Integrated wavelength locking optics
• 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
• 50GHz optical channel spacing compliant for interlay
or future upgrade
• RoHS compliant
Applications:
• Optical Service Channel (OSC) applications in DWDM
transmission systems using optical amplifiers.
1
Data Sheet
Parameters
Parameter
Threshold current (I
th
)
Slope efficiency
2 mW
3 mW
4 mW
High Power
[2]
Conditions
Min
Typ
10
Max
22
0.09
0.13
0.17
0.43
-10
Unit
mA
mW/mA
mW/mA
mW/mA
mW/mA
dB
V
nm
dB
nm
dB
[1]
0.04
0.06
0.08
0.143
RF input reflection coef (S
11
)
Forward voltage
Peak wavelength (λ
p
)
Dispersion penalty
Time averaged spectral line width
Side-mode suppression
Optical rise/fall time
Monitor photo currents
Monitor dark current
Thermistor resistance
Heatpump current
Heatpump voltage
Change of
λ
with laser temp.
Optical spectral window
1.3
[3]
[4]
1.8
1563
2
1527
-20 dB
34
[5]
0.4
40
0.6
125
40
250
360
50
ps
µA
nA
k
mA
V
nm/°C
∆T
= 64°C
8 to 50°C
4.07
20.7
1000
2.4
0.09
∆T
= 64°C
Over life & temperature
including chirp
[6]
-9
+9
GHz
[1] The high power version provides 10 mW peak output power for 175 km applications and 7 mW peak output power for
360 km applications.
[2] 50 measurement system, f = dc - 3 GHz.
[3] Submount temperature between 0°C & 40°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.
So
λ
(
λ −
)
ps
/(
nm
.
km
)
4
λ
2
Data Sheet
Absolute Maximum Ratings
Parameter
Case operating temperature
Laser submount operating temperature
Storage temperature
Laser current above I
th
Laser reverse voltage
Laser reverse current
Monitor diode bias
Heat pump current
Heat pump voltage
Fibre bend radius
30
Min
0
8
-40
Max
70
50
85
100
1.0
10
-10
1
2.4
Unit
°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.
3
Data Sheet
Figure 2: Schematic Diagram.
Connections
Pin #
1
2
3
4
5
6
7
Function
Thermistor
Thermistor
Laser DC bias (-)
Monitor short anode (-)
Monitor cathode (+)
TEC (+)
TEC (-)
Pin #
8
9
10
11
12
13
14
Function
Case ground
Case ground
Monitor long anode (-)
Laser case ground
Laser modulation (-)
Laser case ground
N/C
Instructions for use – LC25ET
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 +10 Monitor anodes, Pin 5 Monitor cathode
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 10 V to Pin 5.
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 1.0 A at 2.4 V.
Pin 8, 9, 11, 13 Case ground
These pins must be grounded in all applications.
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 14 N/C
4
This pin is not connected. It should be grounded if possible.
Data Sheet
Ordering Information
LC25ET [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. LC25ET4532CA-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.
LC25ET4532BA-J28
is a 10 mW 1545.32 nm device with an SC connector for use in a 175 km application.
E.g.
LC25ET4532BB-J28
is a 7 mW 1545.32 nm device with an SC connector for use in a 360 km application.
Lead trimming 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.
LC25ET4532BAK-J28
is a 10 mW 1545.32 nm device with an SC connector and a lead length of 3.81mm typical, for use in
a 175 km application.
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