N4375E 26.5 GHz Single-Mode Lightwave Component Analyzer

General Information

Keysight Technologies’ N4375D Lightwave Component Analyzer (LCA) is the instrument of choice to test 10G Ethernet, FCx8, FCx10 and FCx16 electro-optical components, with up to 26.5 GHz modula­tion range as well as electro-optical components for 40/100GbE and 100 Gb/s coherent transmission.

Modern optical transmission systems require fast, accurate and repeatable characterization of the core electro-optical components, the transmitter, receiver, and their subcomponents (lasers, modulators and detectors), to guarantee performance with respect to modulation bandwidth, jitter, gain, and distortion of the final transceiver.

The N4375D guarantees excellent electro-optical measurement performance through NIST traceable factory calibration chain. In addition a unique new calibration concept significantly reduces time from powering up the LCA until the first calibrated measurement can be made. This increases productivity in R&D and on the manufacturing floor.

The fully integrated “turnkey” solution reduces time to market, compared to the time-consuming development of a self-made setup.

The electrical and optical design of the N4375D is optimized for lowest noise and ripple. In addition, this design makes the accuracy independent of the electrical reflection coefficient. It’s the excellent accuracy and repeatability that improves the yield from tests performed with the N4375D, by narrow­ing margins needed to pass the tested devices. NIST traceability ensures world-wide comparability of test results.

The advanced optical design together with temperature-stabilized transmitter and receiver ensures repeatable measurements over days without recalibration.

Using the advanced measurement capabilities of the network analyzer, all S-parameter related char­acteristics of the device under test, like responsivity, ripple, group delay and 3 dB-cutoff frequency, can be qualified with the new N4375D Lightwave Component Analyzer from 10 MHz to 25.6 GHz.

Key benefits

High absolute and relative accuracy measurements improve the yield of development and production processes. With the excellent accuracy and reproducibility, measurement results can be compared among test locations world wide

High confidence and fast time-to-market with a NIST-traceable turnkey solution

Significantly increased productivity using the fast and easy measurement setup with an unique new calibration process leads to lower cost of test

New switched architecture of optical test set for long-term reliability and stability of test results

Identical LCA software and remote control across the N437xD family simplifies integration and backward compatibility to N437xB/C series

Keysight N4375D 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 sys­tem. However it is necessary to design and qualify subcomponents like modulators and receivers, which are analog by nature, with different parameters. Those parameters are core to the overall system performance.

These electro-optical components significantly influence the overall performance of the transmission system via the following parameters:

3 dB bandwidth of the electro-optical transmission relative frequency response, quantifying the electro-optical shape of the conversion.

Absolute frequency response, relating to the conversion 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 successful operation in the transmission system.

Keysight N4375D Features

Turnkey solution

In today’s highly competitive environment, short time-to-market with high quality is essential for new products. Instead 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 focus resources on faster development and on optimizing the manufacturing process.

In the N4375D 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 components, 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 N4375D.

Easy calibration

An LCA essentially measures the conversion relation between optical and electrical signals. This is why user calibration of such systems can evolve into a time consuming task. With the new calibration process implemented in the N4375D, the tasks that have to be done by the user are reduced to one pure electrical calibration. The calibration with an electrical microwave 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 N4375D’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 components 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 performing 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.

Based on programming examples for VBA with Excel, Keysight VEE and C++, it is very easy for every user to build applications for their requirements.

These examples cover applications like integration of complete LCA measurement se­quences.

Keysight N4375D Specifications

Measurement conditions

Modulation frequency range from 10 MHz to 26.5 GHz

Foreward RF power +5 dBm

Reverse RF power 0 dBm

Number of averages: 1

100 Hz IFBW (“Reduce IF bandwidth at low frequency” enabled) with modulation frequency step size 10 MHz and measurement points on a 10 MHz raster (if not differently stated)

Network analyzer set to “stepped sweep – sweep moves in discrete steps”

All network-analyzer ports configured in normal coupler configuration (“CPLR ARM” to “RCVB B in”, “SOURCE OUT” to “CPLR THRU”)

After full two-port electrical calibration using an Electronic Calibration Module, Keysight N4691B, at constant temperature (± 1 °C) with network analyzer set to –10 dBm electrical output power

Modulator bias optimization set to “every sweep”

Measurement frequency grid equals electrical calibration grid

DUT signal delay ≤ 0.1/IF-BW

Specified temperature range: +20 °C to +26 °C

After warm-up time of 90 minutes

Using high quality electrical and optical connectors and RF cables in perfect condition

Using internal laser source

The optical test set always has angled connectors. Depending on the selected option (-021 straight, -022 angled) the appropriate jumper cable will be delivered. This jumper cable must always be used in front to the optical test set to protect the connectors at the optical test set and is required for performance tests.