N4374B 4.5 GHz Single-Mode Lightwave Component Analyzer for CATV and Radio over Fiber

The Keysight Technologies, Inc. N4374B Lightwave Component Analyzer (LCA) is optimized for the electro-optical S-parameter measurement for Cable TV (CATV) and Radio over Fiber (RoF) or radio frequency over Glass (RFoG) applications.  In modern CATV or RoF/RFoG transmission systems analog sig­nals are directly transmitted over optical fiber. This requires very low distortion of the electro-optical devices at the transmitter and the receiver side. Therefore it is necessary to have very flat transfer characteristic in amplitude and delay. The N4374B LCA is the tool of choice to optimize your design for these parameters. For frequency dependent responsivity measurements the N4374B is the successor of the industry standard 8702 LCA series. It sup­ports 75 Ohm test with a minimum loss pad (MLP). With a completely new design of the optical test set together with the newest ENA based network analyzer, the N4374B guaran­tees excellent electro-optical measurement performance. It’s the excellent accuracy that improves the yield from tests performed with the N4374B, by narrowing margins needed to pass the test­ed devices. NIST traceability ensures world-wide comparability of test results. The fully integrated “turnkey” solution reduces time to market, compared to the time-consuming development of a self-made setup.  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. By optimizing the electrical and optical design of the N4374B for lowest noise and ripple, the accuracy has been improved by more than a factor of 5 compared to the 8702 series LCA and is now independent of the electrical reflection coefficient of the device under test. 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 3dB-cutoff frequency, can be qualified with the new N4374B Lightwave Component Analyzer from 100kHz to 4.5 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 a unique new calibration process leads to lower cost of test. 75 Ohm support Specified phase uncertainty More than 5 times faster than predecessor 8702 series speeds up every test procedure Identical LCA software and remote control across the N437xB family simplifies integration Bias-T included in Network Analyzer   

Keysight N4374B Applications 

In photonic CATV or RoF transmission systems, it is necessary to design and qualify subcomponents like direct modulated lasers 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: 3dB 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.

 Electro-optical components 

The frequency response of amplified or unamplified detector diodes, modulators and directly modulated lasers typically depends on various parameters, 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 parallel the LCA also measures the electrical return loss.  In manufacturing it is important to be able to monitor the pro­cesses regularly to keep up the throughput and yield. In this case the LCA is the tool of choice to monitor transmission character­istics and absolute responsivity of the manufactured device. The remote control of the N4374B offers another tool to improve the productivity by making automated measurements and analysis of the measured data. 

Electrical components 

Electrical components such as amplifiers, filters and transmission 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. The new switched architecture offers direct access to the electrical outputs and inputs of the network-analyzers just by selecting electrical- to electrical measurement mode in the LCA user interface.  

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 N4374B 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 N4374B. 

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 N4374B, the tasks that have to be done by the user are reduced to one pure electrical calibration. The calibration with an electrical calibration module is automated and needs only minimal manual interaction. With the minimum loss pad (MLP) which is part of the LCA shipment the impedance match from 50 Ohm LCA system to 75 Ohm test device can be realized in an easy way. The correction for the 75 Ohm impedance is enabled with one button in the LCA software which uses default data to correct the MLP transfer behavior. For higher accuracy an individual calibration of the MLP can be real­ized with the adaptor removal tool which is part of each ENA-C  

Built-in performance verification 

 The N4374B’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.