Agere Systems 1241, 1243, 1245 DATA SHEET

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1241/1243/1245-Type Uncooled Laser Transmitter

Data Sheet

September 1999

Features

Backward compatible with 1227/1229/1238-Type

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Laser Transmitters
Space-saving, self-contained, 20-pin DIP

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Uses field-proven, reliable InGaAsP MQW laser

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Requires single 5 V power supply

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SONET/SDH compa tible

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Uncooled laser with automatic optical power con-

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trol for constant output power over case tempera­ture range

Offering multiple output power o ptio ns an d SONE T/SDH com­patib ility, the 12 41/1243-Type U ncooled La se r Transmi t ter is
manufactured in a 20-pin, plastic DIP with a single-mode fiber
pigtail.

No thermoel ec tric cooler required; reduces size

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and power consumption
Uses low-power dissipation CMOS technology

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Qualified to meet the intent of Bellcore reliability

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practices
Operates over data rates to 1062.5 Mbits/s (NRZ)

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Operation at 1.3 µm or 1.55 µm wavelength

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Typical average output power options of –11 dBm,

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–8 dBm, –5 dBm, –2 dBm, and 0 dBm
ECL compatible, differential inputs

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Operating temperature range of –40 °C to +85 °C

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Transmitter-disable option

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Applications

Telecommunications

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— Inter- and intraoffice SONET/ITU-T SDH
— Subscriber loop
— Metropolitan area networks

High-speed data communications

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— Fibre channel (FC-0)

Data Sheet

1241/1243/1245-Type Uncooled Laser Transmitter September 1999

Description

The 1241/1243/1245-type Laser Transmitters are
designed for use in transmission systems and high­speed 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-253­CORE requirements, ANSI T1.117-1991 SONET sin­gle-mode, and the ITU-T G.957 and G.958 recommen­dations. (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 operat­ing case temperature range. The automatic power con­trol 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 Fabry­Perot 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. Man­ufactured 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 modula­tion, 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 configu­ration. (See Recommended User I nte rfaces section for
typical connection schemes.) The laser bias and back­facet monitor currents are electrically accessible for
transmitter performance monitoring. The transmitter
optical output may be disabled by a logic-level input.

Functional Overview

Transmitter Circuit Description and
Operation

Figure 1 shows a simplified schematic of the transmit­ter; 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 re ference
level with automatic, temperature-compensated laser
bias, and modulation-current control. A back-facet pho-

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 con­stant 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 o f the laser bias current. This valu e will
change up or down in response t o operati ng tempera­ture, power supply voltage, data pattern, and laser
aging characteristics.

Table 1. Pin Descriptions

Pin Number Name

1 No user connection
2 Laser bias monitor (+)
3 No user connection
4 Laser bias monitor (–)
5V
6V

EE
CC

*

†

*

†

7 Transmitter disable
8V
9V

10 No user connection

CC
CC

†

11 Case ground (RF ground)
12 V

CC

13 Case ground (RF ground)
14 V

EE

15 DATA
16 DATA
17 Laser back-facet monitor (–)
18 V

CC

19 Laser back-facet monitor (+)
20 No user connection

* Pins d esignate d as no user co nnection should not be tie d to

ground or any other circuit potential.

† Lase r back-facet and bi as m on itor funct io ns a re cu stomer-use

optio ns that are not require d for normal operations of the trans­mitter. They are normally used during manufacture and for
diagnostics.

*

*

†

2 Agere Systems Inc.

Data Sheet
September 1999

1241/1243/1245-Type Uncooled Laser

Functional Overview

TRANSMITTER

(continued)

(2)

(+)

(4)

(–)

(19)

(+)

(17)

(–)

(16)

DATA

(15)

DATA

(7)

DISABLE

15 k•

LASER BIAS MONITOR VOLTAGE

15 k•

15 k•

LASER BACK-FACET MONITOR VOLTAGE

15 k•

30 k•

V

– 1.3 V

CC

30 k•

BAND GAP

REFERENCE

INPUT DATA

COMPARATOR

BACK-FACET

DETECTOR

AUTOMATIC POWER

CONTROL CIRCUITRY

MODULATION

CIRCUITRY

I

BF

TEMPERATURE

t

SENSOR

I

BIAS

V

CC

LASER

FIBER PIGTAIL

10 •

I

MOD

1-868(C).h

Figure 1. Simplified Transmitter Schematic Input Data

Input Data

Data enter s the transmitt er through a comparator.
These inputs have internal pull-down resistors to a volt-

. Thi s conf igura-

age reference that is 1.3 V below V

CC

tion allows the transmitter to be dr iven from either a

input signal, the optical signal will be the complement
of the data input signal.

The differental inputs of the 1241 Gbit versions are ter­minated internally with 100 Ω between t he DATA and
DA TA

inputs.
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 sin gle-ended,
however, the input signal voltage should be centered
around V

– 1.3 V to eliminate pulse-width distortion.

CC

With a single-ended input, either input can be used and
the unused input can be left as an open circu i t 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 las er diode on and

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 applica­tions. For burst-mode applications, please contact your
Agere Account Man ager. The minimum data rate
(pseudorandom data, 50% average duty cycle) for the
1241/1243/1245-Type Transmitters is approximately
1 Mbit/s.

an input logic low turns the laser diode off. However, if
the nega tive input is used with a single-ended data

Agere Systems Inc. 3

Data Sheet

1241/1243/1245-Type Uncooled Laser Transmitter September 1999

Functional Overview

Since most applications operate at very high data
rates, high-frequency design techniques need to be
used to ensure optimum performance from the trans­mitter and interfacing circuitry. Input signal paths
should be kept as short and as straight as possible; dif­ferential signal lines should be equal in length, and
controlled-impedance stripline or microstrip construc­tion should always be used when laying out th e printed­wiring board traces for the data lines. The Recom­mended User Inter faces section of this data sheet
shows several methods of interfacing to the transmitter.

(continued)

Power Supplies

The transmitter is configured for operation from either a
single +5 V power supply or a single –5 V power sup­ply . F or positive power supply operation, connect Vcc to
the +5 V power supply and c onnect V
circuit common. For operation from a –5 V power sup­ply, connect V
power supply. Whichever option is chosen, the V
V

connection to the transmitter should be well filtered

EE

to prevent power supply noise from interfering with
transmitter operation.

to ground and connect VEE to the –5 V

CC

to ground or

EE

CC

or

Transmitter Specifications

Connector Opti ons

The standard optical fiber pigtail is 8 µm core single­mode fiber having a 0.036 in. (914 µm) diameter tight­buffered outer-jacket. The standard length is 39 in. ±
4 in. (1 m ± 10 cm) and c an be te rm inated 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 b o th
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-suscepti bility testing and protection-design evalu­ation. 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 wi dely used and, there fore, can be used for compari­son purposes. The HBM ESD withstand voltage estab­lished for the 1241-/1243- T yp e Transmitter is ±1000 V.

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 tun­ing 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 pat­tern eye opening.

Transmitter Processing

The transmitter can withstand normal wave-soldering
processes. The complete transmitter module is not her­metically sealed; therefore, it should not be immersed
in or sprayed with any cleaning so lutio n or solvents.
The process cap and fiber pigtail jacket deformation
temperature is 85 °C. Transmitter pins can be wave­soldered 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
exten sion tube can be used to remove any debris.
Other cleaning procedures are identified in the techni­cal note, Cleaning Fiber-Optic As se mblies (TN95­010LWP).

4 Agere Systems Inc.