Telecommunications SONET/SDH OC-48/STM-16, OC-192/STM-64 Extended and ultralong reach Undersea systems Dense WDM systems Digital videoThe �m D2525P Laser Module is available a 14-pin, hermetic, butterfly package.
The D2525P family of DFB laser modules is designed to be used with a lithium niobate external modulator (see Table 5). The laser module features a polarization-maintaining fiber (PMF) pigtail, enabling to be directly connected to a modulator without the need of a polarization controller. The PMF maintains the polarization of the output light to a consistent orientation. This allows the to be used a CW light source for systems requiring extremely low chirp such as undersea or 10 Gbits/s systems. The module contains a multiquantum-well (MQW), distributedfeedback (DFB) laser. This device nominally has an output power of 10 mW. The wavelength of the laser can be temperature-tuned for more precise wavelength selection by adjusting the temperature of the internal thermoelectric cooler.Features
ITU wavelengths available from --1610.06 nm Integrated optical isolator High-performance, multiquantum-well (MQW), distributed-feedback (DFB) laser Industry-standard, 14-pin butterfly package Hermetic package InGaAs, PIN photodetector back-facet monitor Polarization-maintaining fiber pigtail For use with lithium niobate modulators High reliability Narrow linewidth High optical power available
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.CORE STRESS ROD PRINCIPLE POLARIZATION AXIS CLADDING INNER COATING (SILICON & ACRYLATE)
An integral thermoelectric cooler (TEC) provides stable thermal characteristics. The TEC allows for heating and cooling of the laser chip to maintain a temperature 25 �C for case temperatures from to +70 �C. The laser temperature is monitored by the internal thermistor, which can be used with external circuitry to control the laser chip temperature.
Pin Name Thermistor Laser dc Bias (Cathode) Back-facet Monitor Anode Back-facet Monitor Cathode Thermoelectric Cooler (+)1 Thermoelectric Cooler (�)1 Case Ground Case Ground Case Ground Laser Anode 2 RF Laser Input Cathode Laser Anode 2 Case Ground
An internal, InGaAs, PIN photodiode functions as the backfacet monitor. The photodiode monitors emission from the rear facet of the laser and, when used in conjunction with control circuitry, can control optical power launched into the fiber. Normally, this configuration is used in a feedback arrangement to maintain consistent laser output power.
The laser module is fabricated a 14-pin, hermetic, metal/ ceramic butterfly package that incorporates a bias tee that separates the dc-bias path from the RF input. The RF input has a nominal 25 impedance. The laser module is equipped with Fujikura* polarizationmaintaining fiber (PMF). The fiber is PANDA type and is the same fiber that is used on the Agere Systems Inc. lithium niobate modulators. It has a mode field diameter of 10.5 �m, a cladding diameter �m �3 �m, and a loose tube jacketed fiber �m in diameter. The pigtail is terminated with ST � ferrule. Figure 1 shows the orientation of polarization in the fiber. Agere Systems optoelectronic components are being qualified to rigorous internal standards that are consistent with Telcordia Technologies TR-NWT-000468. All design and manufacturing operations are ISO� 9001 certified. The module is being fully qualified for central office applications.
* Fujikura is a registered trademark of Fujikura Ltd. The ST ferrule key is not aligned to slow axis of fiber. Connector is intended for testing purposes only. Telcordia Technologies is a trademark of Telcordia Technologies Inc. � ISO is a registered trademark of The International Organization for Standardization.
1. A positive current through the thermoelectric heat pump cools the laser. 2. Both leads should be grounded for optimum performance.Figure 2. Circuit Schematic Agere Systems Inc.
Stresses in excess of the absolute maximum ratings can cause permanent damage to the device. These are absolute 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 Laser Reverse Voltage dc Forward Current Operating Case Temperature Range Storage Case Temperature Range* Photodiode Reverse Voltage Photodiode Forward CurrentSymbol VRLMAX IFLMAX TC Tstg VRPDMAX IFPDMAX
To avoid the possibility of damage to the laser module from power supply switching transients, follow this turn-on sequence: 1. All ground connections 2. Most negative supply 3. Most positive supply 4. All remaining connections Reverse the order for the proper turn-off sequence.
The minimum fiber bend radius 1.0 in.(25.4 mm) To avoid degradation in performance, mount the module on the board as follows: 1. Place the bottom flange of the module on a flat heat sink at least 0.5 in. x 1.180 in. x 30 mm) in size. The surface finish of the heat sink should be better than 32 �in. (0.8 �m), and the surface flatness must be better than 0.001 in. (25.4 �m). Using thermal conductive grease is optional; however, thermal performance can be improved 5% if conductive grease is applied between the bottom flange and the heat sink. 2. Mount four #2-56 screws with Fillister heads (M2-3 mm) at the four screw hole locations (see Outline Diagram). The Fillister head diameter must not exceed 0.140 in. (3.55 mm). Do not apply more than 1 in.-lb. of torque to the screws.
CAUTION: This device is susceptible to damage as a result of electrostatic discharge. Take proper precautions during both handling and testing. Follow guidelines such as JEDEC Publication No. 108-A (Dec. 1988). Agere Systems employs a human-body model (HBM) for ESD-susceptibility testing and protection-design evaluation. ESD voltage thresholds are dependent on the critical parameters used to define the model. A standard HBM (resistance 1.5 k, capacitance = 100 pF) is widely used and, therefore, can be used for comparison purposes. The HBM ESD threshold presented here was obtained using these circuit parameters: Parameter Human-body Model Agere Systems Inc. Value >400 Unit V