Data Sheet
September 1999
1241/1243/1245-Type Uncooled Laser Transmitter
Features
s
Backward compatible with 1227/1229/1238-Type
Laser Transmitters
Space-saving, self-contained, 20-pin DIP
Uses field-proven, reliable InGaAsP MQW laser
Requires single 5 V power supply
SONET/SDH compatible
Uncooled laser with automatic optical power con-
trol for constant output power over case tempera-
ture range
No thermoelectric cooler required; reduces size
and power consumption
Uses low-power dissipation CMOS technology
Qualified to meet the intent of Bellcore reliability
practices
Operates over data rates to 1062.5 Mbits/s (NRZ)
Operation at 1.3 µm or 1.55 µm wavelength
Typical average output power options of –11 dBm,
–8 dBm, –5 dBm, –2 dBm, and 0 dBm
ECL compatible, differential inputs
Operating temperature range of –40 °C to +85 °C
Transmitter-disable option
s
s
s
s
s
s
Offering multiple output power options and SONET/SDH com-
patibility, the 1241/1243-Type Uncooled Laser Transmitter is
manufactured in a 20-pin, plastic DIP with a single-mode fiber
pigtail.
s
s
s
s
s
s
s
s
Applications
s
Telecommunications
— Inter- and intraoffice SONET/ITU-T SDH
— Subscriber loop
— Metropolitan area networks
High-speed data communications
— Fibre channel (FC-0)
s
1241/1243/1245-Type Uncooled Laser Transmitter
Data Sheet
September 1999
Description
The 1241/1243/1245-type Laser Transmitters are
designed for use in transmission systems and high-
speed data communication applications. Used in
intraoffice and intermediate-reach applications, the
transmitters are configured to operate at SONET rates
up to OC-12, as well as at ITU-T synchronous digital
hierarchy (SDH) rates up to STM-4. Specific versions
are also capable of operating up to 1062.5 Mbits/s.
The transmitter meets all present Bellcore GR-253-
CORE requirements, ANSI T1.117-1991 SONET sin-
gle-mode, and the ITU-T G.957 and G.958 recommen-
dations. (See Table 5 to select transmitters for the
various SONET/SDH segments.)
The transmitter requires a single power supply (+5 V or
–5 V) and operates over data rates of 1 Mbits/s to
622 Mbits/s (NRZ). Automatic power control circuitry
provides constant optical output power over the operat-
ing case temperature range. The automatic power con-
trol circuitry also compensates for laser aging. The
optical wavelength tolerance at 25 °C is 1310 nm. The
temperature coefficient of wavelength for 1.3 µm Fabry-
Perot transmitters (1241-Type) is approximately
0.4 nm/°C. The temperature coefficient of wavelength
for 1.3 µm and 1.55 µm distributed-feedback (DFB)
transmitters (1243/1245-Type) is approximately
0.1 nm/°C.
Transmitters are available for operation over several dif-
ferent temperature ranges from –40 °C to +85 °C. Man-
ufactured in a 20-pin DIP the transmitter consists of a
,
hermetic, InGaAs laser and a single CMOS driver IC.
The low-power consumption circuit provides modula-
tion, automatic optical output power control, and data
reference. The module can be driven by either ac- or
dc-coupled data in single-ended or differential configu-
ration. (See Recommended User Interfaces section for
typical connection schemes.) The laser bias and back-
facet monitor currents are electrically accessible for
transmitter performance monitoring. The transmitter
optical output may be disabled by a logic-level input.
todetector diode within the laser module provides an
indication of the laser's average optical output power.
The back-facet diode current is accessible as a voltage
proportional to photocurrent through pins 17 and 19 on
the transmitter. The back-facet diode also forms part of
the feedback control circuit, which helps maintain con-
stant output power.
The laser bias current is accessible as a dc-voltage by
measuring the voltage developed across pins 2 and 4
of the transmitter. Dividing this voltage by 10
Ω
will
yield the value of the laser bias current. This value will
change up or down in response to operating tempera-
ture, power supply voltage, data pattern, and laser
aging characteristics.
Table 1. Pin Descriptions
Pin Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Name
No user connection
*
Laser bias monitor (+)
†
No user connection
*
Laser bias monitor (–)
†
V
EE
V
CC
Transmitter disable
V
CC
V
CC
No user connection
†
Case ground (RF ground)
V
CC
Case ground (RF ground)
V
EE
DATA
DATA
Laser back-facet monitor (–)
*
V
CC
Laser back-facet monitor (+)
*
No user connection
†
Functional Overview
Transmitter Circuit Description and
Operation
Figure 1 shows a simplified schematic of the transmit-
ter; pin information is listed in Table 1. The laser within
the transmitter is driven by a single CMOS integrated
circuit, which provides the input data signal reference
level with automatic, temperature-compensated laser
bias, and modulation-current control. A back-facet pho-
2
* Pins designated as no user connection should not be tied to
ground or any other circuit potential.
† Laser back-facet and bias monitor functions are customer-use
options that are not required for normal operations of the trans-
mitter. They are normally used during manufacture and for
diagnostics.
Agere Systems Inc.
Data Sheet
September 1999
1241/1243/1245-Type Uncooled Laser
Functional Overview
(continued)
V
CC
LASER
BACK-FACET
DETECTOR
(2)
(+)
LASER BIAS MONITOR VOLTAGE
(4)
(–)
15 k•
(+)
(19)
15 k•
15 k•
FIBER PIGTAIL
LASER BACK-FACET MONITOR VOLTAGE
(17)
(–)
15 k•
BAND GAP
REFERENCE
AUTOMATIC POWER
CONTROL CIRCUITRY
I
BF
10 •
(16)
DATA
30 k•
V
CC
– 1.3 V
INPUT DATA
COMPARATOR
t
TEMPERATURE
SENSOR
MODULATION
CIRCUITRY
I
BIAS
I
MOD
30 k•
(15)
DATA
TRANSMITTER
DISABLE
(7)
1-868(C).h
Figure 1. Simplified Transmitter Schematic Input Data
Input Data
Data enters the transmitter through a comparator.
These inputs have internal pull-down resistors to a volt-
age reference that is 1.3 V below V
CC
. This configura-
tion allows the transmitter to be driven from either a
single-ended or a differential input signal. Since the
input is a comparator instead of a gate, the absolute
input signal levels are not important when the inputs
are driven differentially. When driven single-ended,
however, the input signal voltage should be centered
around V
CC
– 1.3 V to eliminate pulse-width distortion.
With a single-ended input, either input can be used and
the unused input can be left as an open circuit due to
the internal reference shown in Figure 1. The optical
output signal will be in the same sense as the input
data—an input logic high turns the laser diode on and
an input logic low turns the laser diode off. However, if
the negative input is used with a single-ended data
Agere Systems Inc.
input signal, the optical signal will be the complement
of the data input signal.
The differental inputs of the 1241 Gbit versions are ter-
minated internally with 100
Ω
between the DATA and
DATA inputs.
Minimum Data Rate
Because the modulation and bias control circuitry are
influenced by the input data pattern, the standard
transmitter cannot be used in burst-mode type applica-
tions. For burst-mode applications, please contact your
Agere Account Manager. The minimum data rate
(pseudorandom data, 50% average duty cycle) for the
1241/1243/1245-Type Transmitters is approximately
1 Mbit/s.
3
1241/1243/1245-Type Uncooled Laser Transmitter
Data Sheet
September 1999
Functional Overview
(continued)
Since most applications operate at very high data
rates, high-frequency design techniques need to be
used to ensure optimum performance from the trans-
mitter and interfacing circuitry. Input signal paths
should be kept as short and as straight as possible; dif-
ferential signal lines should be equal in length, and
controlled-impedance stripline or microstrip construc-
tion should always be used when laying out the printed-
wiring board traces for the data lines. The Recom-
mended User Interfaces section of this data sheet
shows several methods of interfacing to the transmitter.
Connector Options
The standard optical fiber pigtail is 8 µm core single-
mode fiber having a 0.036 in. (914 µm) diameter tight-
buffered outer-jacket. The standard length is 39 in. ±
4 in. (1 m ± 10 cm) and can be terminated with either
an SC or FC-PC optical connector. Other connector
options may be available on special order. Contact your
Agere Account Manager for ordering information.
Handling Precautions
CAUTION: This device is susceptible to damage as
a result of electrostatic discharge (ESD).
Take proper precautions during both
handling and testing. Follow guidelines
such as JEDEC Publication No. 108-A
(Dec. 1988).
Although protection circuitry is designed into the
device, take proper precautions to avoid exposure to
ESD. Agere employs a human-body model (HBM) for
ESD-susceptibility testing and protection-design evalu-
ation. ESD voltage thresholds are dependent on the
critical parameters used to define the model. A stan-
dard HBM (resistance = 1.5 kΩ, capacitance = 100 pF)
is widely used and, therefore, can be used for compari-
son purposes. The HBM ESD withstand voltage estab-
lished for the 1241-/1243-TypeTransmitter is ±1000V.
Power Supplies
The transmitter is configured for operation from either a
single +5 V power supply or a single –5 V power sup-
ply. For positive power supply operation, connect Vcc to
the +5 V power supply and connect V
EE
to ground or
circuit common. For operation from a –5 V power sup-
ply, connect V
CC
to ground and connect V
EE
to the –5 V
power supply. Whichever option is chosen, the V
CC
or
V
EE
connection to the transmitter should be well filtered
to prevent power supply noise from interfering with
transmitter operation.
Transmitter Specifications
Optical Output Power
During manufacture, the optical output power of every
transmitter is tuned to the typical value specified in the
data sheet for that particular transmitter code. The tun-
ing is performed at room ambient and a power supply
voltage of 5 V. The minimum and maximum values
listed in the data sheet for each code group reflect the
worst-case limits that the transmitter is expected to
operate within over its lifetime and over the allowed
power supply and the operating temperature range.
Every transmitter shipped receives a final test, which
includes a SONET eye-mask test at either the OC-3
(STM-1) data rate of 155.52 Mbits/s, the OC-12 (STM4)
data rate of 622.08 Mbits/s, or the fibre channel FC-0
data rate of 1062.5 Mbits/s. The eye-mask test is
meant to examine the performance of the transmitter's
output optical waveform relative to a minimum data pat-
tern eye opening.
Transmitter Processing
The transmitter can withstand normal wave-soldering
processes. The complete transmitter module is not her-
metically sealed; therefore, it should not be immersed
in or sprayed with any cleaning solution or solvents.
The process cap and fiber pigtail jacket deformation
temperature is 85 °C. Transmitter pins can be wave-
soldered at maximum temperature of 250 °C for
10 seconds.
Installation Considerations
Although the transmitter features a robust design, care
should be used during handling. The optical connector
should be kept free from dust, and the process cap
should be kept in place as a dust cover when the
device is not connected to a cable. If contamination is
present on the optical connector, canned air with an
extension tube can be used to remove any debris.
Other cleaning procedures are identified in the techni-
cal note,
Cleaning Fiber-Optic Assemblies
(TN95-
010LWP).
Agere Systems Inc.
4
Data Sheet
September 1999
1241/1243/1245-Type Uncooled Laser
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 operations sections of the data sheet. Exposure to absolute maximum ratings for extended
periods can adversely affect device reliability.
Parameter
Supply Voltage
*
Operating Case Temperature Range
†
Storage Case Temperature Range
Lead Soldering Temperature/Time
Relative Humidity (noncondensing)
Minimum Fiber Bend Radius
Symbol
—
T
C
T
stg
—
RH
—
Min
—
–40
–40
—
—
1.00 (25.4)
Max
5.5
85
85
250/10
85
—
Unit
V
°C
°C
°C/s
%
in. (mm)
* With V
EE
connected to –5 V, V
CC
must be at 0 V; with V
CC
connected to +5 V, V
EE
must be at 0V.
†
Specification depends upon the code ordered. The device is capable of a cold start at –40 °C; specifications are met
after a warm-up time determined by the system thermal design.
Characteristics
Minimum and maximum values specified over operating case temperature range at 50% duty cycle data signal and
end of life (EOL).Typical values are measured at beginning-of-life (BOL) room temperature unless otherwise noted.
Table 2. Electrical Characteristics
Parameter
Power Supply Voltage
1
Power Supply Current Drain
Input Data Voltage:
2
Low
High
Input Transition Time
3
Transmitter Disable Voltage
4
Transmitter Enable Voltage
Output Disable Time
5
Output Enable Time
6
Laser Bias Voltage
7
Laser Monitor Voltage (50% duty cycle)
8
Symbol
V
I
TOTAL
V
IL
V
IH
t
I
V
D
V
EN
t
D
t
EN
V
B
V
BF
Min
4.75
—
–1.81
–1.16
—
V
CC
– 2.0
V
EE
—
—
0.01
0.01
Typ
5.0
30
—
—
t/4
—
—
—
—
0.06
0.05
Max
5.50
130
–1.47
–0.88
—
V
CC
V
EE
+ 0.8
0.20
2.00
0.70
0.20
Unit
V
mA
V
V
ns
V
V
µs
µs
V
V
1. With V
EE
connected to –5V, V
CC
must be at 0 V; with V
CC
connected to +5 V, V
EE
must be at 0 V.
2. Input measured from V
CC
with 50
Ω
load to (V
CC
– 2 V). 10K, 10K H, and 100K ECL compatible.
3. Between 10% and 90% (50% duty cycle) where t is the bit period in ns.
4. The transmitter is normally enabled and only requires an external voltage to disable.
5. Time measured from rising edge of disable signal until optical output (laser diode) has turned off.
6. Time measured from falling edge of enable signal until optical output has stabilized at nominal output power level.
7. The laser bias current is obtained by dividing the bias voltage by the 10
Ω
current-sensing resistors. (See Figure 1.) When measuring these
voltages or using them in conjunction with alarm circuits, use a high-input impedance device.
8. The laser back-facet monitor voltage is a scaled output that tracks the transmitter optical output power.
Agere Systems Inc.
5
京公网安备 11010802033920号
EEWORLD
