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Lucent Technologies Inc.

Data Sheet

February 2000

Isolated DFB Laser Module

1.5

µm D2500-Type Digital

Description

The D2500-Type Digital Isolated DFB Laser Module

contains an internally cooled, InGaAsP, MQW, distrib-

uted-feedback (DFB) laser designed for 1.5

µm appli-

cations. The laser is designed to be used in OC-12/

STM-4 (622 Mbits/s) and OC-48/STM-16 (2.488 Gbits/

s) for long-reach and extended-reach applications. It is

also capable of low dispersion penalties (<2 dB) for use

with fiber spans exceeding 170 km (3000 ps/nm).

The device is available with an average output power of

0 dBm (3 dBm peak), which meets the SONET/SDH

standard. To eliminate the need for optical amplifiers in

some applications, the module can also be ordered

with higher output powers.

Controlled Feedback

The module contains an internal optical isolator that

suppresses optical feedback in laser-based, fiber-optic

systems. Light reflected back to the laser is attenuated

a minimum of 30 dB.

Controlled Temperature

An integral thermoelectric cooler (TEC) provides stable

thermal characteristics. The TEC allows for heating and

cooling of the laser chip to maintain a temperature of

25

°C for case temperatures from –40 °C to +70 °C.

The laser temperature is monitored by the internal ther-

mistor, which can be used with external circuitry to con-

trol the laser chip temperature.

Controlled Power

An internal, InGaAs, PIN photodiode functions as the

back-facet monitor. The photodiode monitors emission

from the rear facet of the laser and, when used in con-

junction with control circuitry, can control optical power

launched into the fiber. Normally, this configuration is

used in a feedback arrangement to maintain the aver-

age laser output power.

Standard Package

The laser module is fabricated in a 14-pin, hermetic,

metal/ceramic butterfly package. The package also

incorporates a bias tee that separates the dc-bias path

from the RF input. The RF input has a nominal 25

Ω

impedance. The laser module is equipped with a sin-

gle-mode fiber with an 8

µm core and 125 µm cladding.

The minimum pigtail length is 39.4 in. (100 cm); the

minimum bend radius is 1.18 in. (30 mm).

The pigtail is a 900

µm tight buffer fiber. Various con-

nector and pigtail options are available.

Lucent Technologies Microelectronics Group optoelec-

tric components are qualified to rigorous internal stan-

dards that are consistent with

Telcordia Technologies

TR-NWT-000468. All design and manufacturing opera-

tions are

ISO * 9001 certified. The module is fully quali-

fied for central office applications.

*

ISO is a registered trademark of The International Organization for

Standardization.

Pin Information

* A positive current through the thermoelectric heat pump cools the

laser.

† Both leads should be grounded for optimum performance.

Top view.

Figure 1. Circuit Schematic

Pin

Name

1

Thermistor

2

Thermistor

3

Laser dc Bias (cathode) (–)

4

Back-facet Monitor Anode (–)

5

Back-facet Monitor Cathode (+)

6

Thermoelectric Cooler (+)*

7

Thermoelectric Cooler (–)*

8

Case Ground

9

Case Ground

10

Case Ground

11

12

RF Laser Input Cathode (–)

13

14

Case Ground

1-567

TEC

L1

160 nH

ISOLATOR

R1

20

Ω

PACKAGE

GROUNDS

–+

+

–

–

+–

+

76

5

4

3

2

1

8

9

10

11

12

13

TH

10 k

Ω

14