Data Sheet

8

Pin Definitions

Pin 1 MZ data DC Bias input and Pin 2 MZ data-bar DC

Bias input

DC bias voltages for data and data-bar MZ arms. These pins

must be connected to a low noise negative DC voltage,

typically around -2V (WRT case). These voltages are defined

for each Tx in the deliverable data. A precision voltage source

must be used, which is capable of sourcing up to 10mA to

each pin. Refer to Bookham applications note AN0130 for

circuit implementation and filtering suggestions.

Pin 3

Connect to ground.

Pin 4 Bias Control Tap

The MZ bias control tap pin must be biased to -5V.

The supply should be regulated if the device is used

in mode 1 as the monitor diode responsivity is voltage

dependent.

Pins 5, 7 and 9 Ground

Package ground connections.

Pin 6 MZ Data-bar modulation input and Pin 8 MZ Data

modulation input

Operation is typically using differential electrical drive voltages

applied to both the Data and Data-bar MZ Modulator inputs.

Typical amplitude is 2.0V peak-to-peak. AC RF coupling must

be used.

Pin 10 TEC (-) and Pin 11 TEC (+)

The LMC10 contains a Peltier heatpump. Applying a negative

voltage on Pin 10 with respect to Pin 11 will cause the

internal optics to be cooled relative to the case temperature.

Reversing the applied voltage will cause the internal

structures to be heated. The heatpump must be used in

a feedback controlled circuit in conjunction with the

internal thermistor.

Pin 12 Laser Anode

The laser is operated with a forward bias current, the laser

cathode being connected internally to case ground.

Pin 13 Thermistor

The thermistor is used in the TEC control loop for keeping the

internal temperature at a constant value. It has a nominal

resistance of 10k Ohms at a temperature of 25ºC and is not

polarity sensitive, although one side of the thermistor is

connected to package ground. Operating current should be

limited to less than 100µA to prevent self heating errors.

The exact thermistor value is supplied with each Tx as

part of the deliverable test data to ensure the correct

operating wavelength.

Pin 14 Back Facet Monitor Diode Anode (Etalon)

The signal from this diode carries the spectral response of the

wavelength filter.

Pin 15 Back Facet Monitor Diode Common Cathode

Common connection for monitor diode cathodes.

Pin 16 Back Facet Monitor Diode Anode (Reference)

The signal from this diode is the reference signal and

indicates the power of the rear facet of the laser. The signals

from the reference and etalon monitor diodes are used in a

control loop to maintain the wavelength of the laser at the

defined lock point.

Operating the LMC10NEG

Control Schemes for the LMC10NEG

Arm DC Bias Voltage Control

A dynamic control scheme can be implemented to maintain

the bias points on the left and right arms of the MZ modulator

at the quadrature point. This will maintain the output pulse

train with a 50% eye crossing level. The control circuit needs

to track any over life change in the bias points, thereby

maintaining the 50% eye crossing condition.

Benefits of Using Control Schemes

The product can be used without the control scheme as

discussed above. But there are benefits of implementing

the control loop:

Maintaining the optical eye crossing to 50% through the life of

the product will minimise the variation in extinction ratio and

reduce variations in link dispersion penalty.

Summary

For more demanding applications at higher link lengths or

tighter link budgets the LMC10NEG may be used with a

dynamic control scheme which will provide MZ arm bias point

control for 50% optical eye crossing.

Use of the BCT in a control loop can offer improved optical

eye shape stability compared to open loop performance.