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Agilent N4373C Applications

In digital photonic transmission systems, the performance

is ultimately determined by Bit Error Ratio Test (BERT). As

this parameter describes the performance of the whole sys-

tem, it is necessary to design and qualify subcomponents

like modulators and PIN detectors, which are analog by na-

ture, with different parameters that reflect their individual

performance.

These components significantly influence the overall perfor-

mance of the transmission system with the following pa-

rameters:

3dB bandwidth of the electro-optical transmission.

Relative frequency response, quantifying the electro-

optical shape of the conversion.

Absolute frequency response, relating to the conver-

sion efficiency of signals from the input to the output,

or indicating the gain of a receiver.

Electrical reflection at the RF port.

Group delay of the electro-optical transfer function.

Only a careful design of these electro-optical components

over a wide modulation signal bandwidth guarantees suc-

cessful operation in the transmission system.

Electro-optical components

The frequency response of detector diodes, modulators and

directly modulated lasers typically depends on various pa-

rameters, like bias voltages, optical input power, operating

current and ambient temperature. To determine the optimum

operating point of these devices, an LCA helps by making

a fast characterization of the electro-optic transfer function

while optimizing these operating conditions.

In manufacturing it is important to be able to monitor the

processes in regular time slots to keep up the throughput

and yield. In this case the LCA is the tool of choice to moni-

tor transmission characteristic and absolute responsivity of

the manufactured device.

Electrical components

Electrical components such as amplifiers, filters and trans-

mission lines are used in modern transmission systems and

require characterization to ensure optimal performance.

Typical measurements are bandwidth, insertion loss or gain,

impedance match and group delay.

Agilent N4373C Features

Turnkey solution

In today’s highly competitive environment, short time-to-

market with high quality is essential for new products. In-

stead of developing a home-grown measurement solution,

which takes a lot of time and is limited in transferability and

support, a fully specified and supported solution helps to fo-

cus resources on faster development and on optimizing the

manufacturing process.

In the N4373C all optical and electrical components are

carefully selected and matched to each other to minimize

noise and ripple in the measurement traces. Together with

the temperature stabilized environment of the core com-

ponents, this improves the repeatability and the accuracy

of the overall system. Extended factory calibration data at

various optical power levels ensures accurate and reliable

measurements that can only be achieved with an integrated

solution like the N4373C.

Easy calibration

An LCA essentially measures the conversion relation be-

tween optical and electrical signals. This is why user cali-

bration of such systems can evolve into a time consuming

task. With the new calibration process implemented in the

N4373C, the tasks that have to be done by the user are re-

duced to one pure electrical calibration. The calibration with

an electrical calibration module is automated and needs only

minimal manual interaction.

Built-in performance verification

Sometimes it is necessary to make a quick verification of the

validity of the calibration and the performance of the system.

The N4373C’s unique calibration process allows the user to

perform a self-test without external reference devices. This

gives full confidence that the system performance is within

the user’s required uncertainty bands.

State-of-the-art remote control

Testing the frequency response of electro-optical compo-

nents under a wide range of parameters, which is often

necessary in qualification cycles, is very time consuming.

To support the user in minimizing the effort for perform-

ing this huge number of tests, all functions of the LCA can

be controlled remotely via LAN over the state-of-the-art

Microsoft .NET or COM interface. This interface is identical

for all LCA of the N437xB/C series.

Based on programming examples for VBA with Excel, Agi-

lent VEE and C++, it is very easy for every user to build ap-

plications for their requirements.

These examples cover applications like integration of com-

plete LCA measurement sequences.