Data Sheet, Rev. 4
June 2001
A1751A DWDM Analog
Forward-Path or Return-Path Laser Modules
Description
The A1751A laser module is a dense wavelength-
division multiplexing (DWDM) laser for analog appli-
cations. It features a distributed-feedback (DFB) chip
that has been designed specifically for radio fre-
quency (RF) applications. The A1751A laser module
has a wide temperature range for reliable perfor-
mance in harsh node environments and narrow
transmitter designs. It also features low adiabatic
chirp to maximize signal quality in short and long
lengths of fiber. The laser’s excellent inherent linear-
ity minimizes degradation of the broadcast signals
caused by the quadrature amplitude modulation
(QAM) channels.
Features
s
s
s
s
s
s
s
Higher temperature rating
Excellent linearity
Standard ITU wavelengths
Advanced analog chip design
Tested for forward and return path applications
Reduces equipment requirements in the hub
Exceeds
Telcordia Technologies*
468 specifica-
tion.
Wavelength-division multiplexing is being designed
into cable television architectures. DWDM, a method
for delivering targeted QAM signals to different loca-
tions, allows multiple signal sets to be combined onto
a single strand of fiber for transmission from a head-
end to a hub. At the hub, individual QAM signals can
be selected and combined with broadcast analog
channels. The versatile A1751A DWDM laser module
reduces cable network architecture fiber needs and
lessens equipment requirements in the hub.
The A1751A is available in a wide range of standard
ITU wavelengths. The lasers are offered as either for-
ward-path (40 MHz—860 MHz) or return-path
(5 MHz—210 MHz) modules.
Applications
s
s
s
s
Node capability
Narrow transmitter housing
Networks with limited fiber
Architectures using separate optical wavelengths
to carry targeted services
*
Telcordia Technologies
is a trademark of Telcordia Technologies,
Inc.
A1751A DWDM Analog
Forward-Path or Return-Path Laser Modules
Data Sheet, Rev. 4
June 2001
Absolute Maximum Ratings
Stresses in excess of the absolute maximum ratings can cause permanent damage to the device. These are abso-
lute stress ratings only. Functional operation of the device is not implied at these or any other conditions in excess
of those given in the operational sections of the data sheet. Exposure to absolute maximum ratings for extended
periods can adversely affect device reliability.
Parameter*
Operating Case Temperature Range
Storage Temperature Range
Monitor Photodiode Reverse Voltage
Laser Forward Current
Reverse Voltage (Laser)
TEC Current
RF Input Power
Symbol
T
C
Tstg
V
MPD
I
F
V
R
I
TEC
P
RFIN
Min
–40
–40
—
—
—
—
—
Max
85
85
10
150
2
1.7
62
Unit
°C
°C
V
mA
V
A
dBm V
* The device can withstand continuous exposure to the specified limits without damage.
Characteristics
Table 1. Key Characteristics
Parameter
Frequency Range:
1
Return Path
Forward Path
Frequency Response:
1
5 MHz—210 MHz
40 MHz—860 MHz
RF Return Loss:
1
5 MHz—210 MHz
40 MHz—860 MHz
Optical Output Power
Laser Relative Intensity
Noise
Composite Second Order
2, 3
Composite Triple Beat
2, 4
Available Wavelengths
Wavelength Drift
5
Symbol
F
Conditions
—
5
40
—
I
F
= 60 mA,
T
OP
= 25 °C
I
F
= 60 mA,
—
—
6, 8, or
10
—
—
—
1527.94
—
>16
>16
—
<
–155
—
—
—
—
—
—
—
—
–50
–60
1563.1
0.04
dB
dB
mW
dB/Hz
dBc
dBc
nm
nm
—
—
—
—
±0.5
±0.5
210
860
—
—
Min
Typ
Max
Unit
MHz
MHz
MHz
dB
dB
RL
RF
P
O
RIN
CSO
CTB
λ
λ∆
I
F
= I
OP
I
F
= I
TH
+ 70 mA,
T = 25 °C
I
F
= I
OP
OMI = 10%
,
I
F
= I
OP
OMI = 10%
,
I
P
= I
OP
T = T
OP
,
I
F
= 60 mA,
T = T
OP,
T
C
varied from min—>max
I
F
= 60 mA,
T
OP
= 25 °C,
measured at 500 MHz
I
F
= I
OP
Adiabatic Chirp
FM
40
—
100
MHz/mA
Operating Case
Temperature Range
T
C
–40
—
85
°C
1. Tested in a 50
Ω
resistively matched system.
2. Eight channel loading with 10% OMI and 40 km fiber length.
3. Measured at 42 MHz.
4. Measured at 553.25 MHz, 577.25 MHz, and 595.25 MHz.
5. Change in wavelength as case temperature is changed.
2
Agere Systems Inc.
Data Sheet, Rev. 4
June 2001
A1751A DWDM Analog
Forward-Path or Return-Path Laser Modules
Characteristics
(continued)
Table 2. Additional Characteristics
Parameter
Bias Current
1
Threshold Current
Slope Efficiency
2
Monitor Photocurrent
Operating Chip Temperature
3
TEC Current
Symbol
I
B
I
TH
η
I
MON
T
OP
I
TEC
Conditions
BOL
25 °C, BOL
I
P
= I
TH
+ 20 and
I
TH
+ 60
I
OP
= 0 mA, V
RM
= 5 V,
T
OP
= 25 °C
I
F
= I
OP
–40
°C <
T
C
<
85
°C,
T
OP
= 15 °C—35 °C,
I
F
= 60 mA
T
OP
= 15 °C—35 °C over T
C
T
OP
= 25 °C
T
C
I
F
= I
OP
Min
—
—
0.10
10
18
–1.5
Max
120
30
—
200
35
1.5
Unit
mA
mA
mW/mA
µA/mW
°C
A
TEC Voltage
Thermistor Resistance
Optical Return Loss
Side Mode Suppression Ratio
V
TEC
R
TH
RL
SMSR
–2.5
—
40
30
3.8
10.5
—
—
V
kΩ
dB
dB
1. Bias point at which all specifications apply.
2. For 10 mW output power. Minimum slope efficiency is lower for lower-power lasers.
3. Chip temperature at which wavelength specification is met. Operating chip temperature is reported for each laser.
Electrical Schematics
1
ISOLATOR
2
NC
14
13
(+)
3
12
(–)
(–)
4
11
(+)
(+)
5
NC
10
(+)
6
CASE
GROUND
CASE
GROUND
9
(–)
7
TEC
8
1-1233(F)
Figure 1. A1751A Laser Schematic
Agere Systems Inc.
3
A1751A DWDM Analog
Forward-Path or Return-Path Laser Modules
Data Sheet, Rev. 4
June 2001
Electrical Schematics
(continued)
14
NC
13
LASER
COMMON (+)
LASER
MODULATION (–)
LASER
COMMON (+)
THERMISTOR
1
2
THERMISTOR
3
200
Ω
4
SEE
FIGURE 4
3.3
µH
39 nH
0.01
µf
SEE
FIGURES
3A AND 3B
12
dc LASER
BIAS
MPD ANODE
CASE GROUND
11
10
NC
9
MPC CATHODE
5
1000 pf
CASE
GROUND
CASE
GROUND
6
TEC (+)
7
TEC (–)
0.01
µf
0.01
µf
1000 pf
8
1-1234(F)
Figure 2. A1751A Circuit Schematic
0.01
µf
C7
3:5
T1*
2
3
SEE PIN 12,
FIGURE 2
0.5 pF—2.5 pF
R1
37.5
Ω
SEE PIN 12,
FIGURE 2
R2
37.5
Ω
1-1238F.b
VSWR
Figure 3b. Resistive-Matched Configuration
1 pF—
5 pF
FREQUENCY
RESPONSE
*T1 (75
Ω)
3:5.
1-1238F.a
0.01
µf
0.01
µf
Figure 3a. Impedance-Matched Configuration
4
Agere Systems Inc.
Data Sheet, Rev. 4
June 2001
A1751A DWDM Analog
Forward-Path or Return-Path Laser Modules
Electrical Schematics
(continued)
TEC
CONSTANT
ALARM
1
THERMISTOR
2
THERMISTOR
3
200
Ω
4
1000 pf
5
MPC CATHODE
1000 pf
6
TEC (+)
0.01
µf
7
TEC (–)
0.01
µf
1-1238F.c
J2
39 nH
0.01
µf
dc LASER
BIAS
MPD ANODE
CASE GROUND
3.3
µH
1 THERMISTOR
2 THERMISTOR
3 dc LASER BIAS
4 MPD ANODE (CASE GROUND)
5 MPC CATHODE
6 TEC (+)
7 TEC (–)
8 GND
9 GND
10 GND
Note: When ordering the dc set, the following boards are included: alarm board, 9108-004; TEC board, 9028-004; constant current, 9383-004.
Figure 4. dc Set (Agere Systems-Supplied Option)
Agere Systems Inc.
5
