Optical Spectrum Analysis

| Information and Communication Technology

Optical spectrum analyser with short and mid wavelength infrared test and analysis capabilities

Yokogawa has launched new Optical Spectrum Analysers covering a wide range of wavelengths

The latest AQ6375E and AQ6376E models from Yokogawa Test & Measurement combine both short and mid wavelength infrared with extreme optical precision to help with the development of measurement lasers-

The two new optical spectrum analysers (OSAs) were launched to fulfil the market demands for an instrument that is capable of measuring a wide range of wavelengths to meet new needs in optical product development and manufacturing.

The Yokogawa AQ6375E and AQ6376E are the only grating based Optical Spectrum Analysers that cover SWIR (Short-Wavelength Infra Red) over 2 μm and MWIR (Mid-Wavelength Infra Red) over 3 μm with world class optical performance.

Choice of four variants

Building on the past history of Yokogawa’s AQ6375B and AQ6376 OSAs, the new OSAs are offered in four versions.

The AQ6375E Standard has a wavelength range of 1200-2400nm; the AQ6375E Extended Wavelength version has a wavelength range of 1000-2500nm; the AQ6375E Limited version has a wavelength range of 1200-2400nm (with reduced wavelength resolution); and the AQ6376E Standard has a wavelength range of 1500-3400nm – without the resolution reduction.

The choice of wavelengths available gives developers increased flexibility to apply the OSAs in a wide range of applications. These include environmental measurement and gas sensing, where the AQ637xE can be used in the measurement of gas absorption spectra and the characterisation of light sources used in Laser Absorption Spectroscopy.

Other major uses for the new OSAs are medical care and biotechnology as well as industrial laser applications.

Typical applications will include the development and measurement of lasers; the characterisation of broadband light sources such as supercontinuum light sources; optical passive devices; and optical fibres.

According to Terry Marrinan, Yokogawa Test & Measurement’s Vice President & Chief Marketing Officer, the new AQ637xE has been launched to give developers and manufacturers greater flexibility in the range of wavelengths they can measure, all in one highly accurate and very useable family of OSAs.

“The AQ637xE will extend the number of optical products that can be analysed, both in development applications and in production, bringing feature rich, high accuracy measurement to all stages of the process,” he goes on to explain.

Maximising Accuracy

The AQ637xE incorporates numerous features that contribute to achieving maximum accuracy. The free space optical input offers single-mode fibre for the SWIR and MWIR regions and MMF (Multi Mode Fibre) up to 400 µm) on the same OSA. The small variation in insertion loss at the input connector increases measurement repeatability, while the lack of physical contact with the connecting fibres ensures they avoid damage.

Also included is a built-in calibration light source for optical alignment and wavelength calibration. This maintains high optical performance by compensating for deviations in the optical axis caused by vibrations and impacts as well as wavelength deviations caused by changes in ambient temperature.

The AQ637xE instrument also uses an air purging feature to compensate for another cause of possible error. In the SWIR and MWIR region, there are wavelengths where light shows strong absorptions due to the presence of water vapour and carbon dioxide, which can both disturb the spectral measurement.

By continuously supplying pure purge gas such as nitrogen to the monochromator through dedicated connectors on the back panel, the AQ637xE can reduce the influence of light absorptions on the measurement.

High order diffracted light is also compensated for through a built-in cut filter in all versions except the AQ6375E-01 limited model. This is required because the monochromator generates high order diffracted light, which has wavelengths equal to the integral multiples of the input wavelength. The built-in filters reduce this higher-order diffracted light, minimising its influence on the accuracy of the measurement.

Analysis functions

To analyze results, the AQ637xE has built-in analysis functions to characterize optical spectrum from a variety of optical systems and devices, such as WDM system, DFB-LD, EDFA, and filters.

Analysis functions include: DFB-LD; FP-LD; LED; Spectral width (peak/notch); SMSR; Optical power; WDM (OSNR); EDFA (Gain and NF); Filter (peak/bottom) and WDM filter (peak/bottom).

To improve measurement efficiency and productivity, the AQ637xE features an application (APP) mode, transforming a versatile OSA into a machine dedicated to a device under test (DUT).

APP mode provides a DUT-specific user interface that allows the user to move from configuration settings to test results without the need to know the wide variety of OSA settings. The AQ637xE comes pre-installed with several basic applications such as WDM test, DFB-LD test, and FP-LD test. A guide through wizard leads the user through an easy set up process for specific measurements and analysis.

New or additional testing applications will be made available for download from the Yokogawa website and can be added to the AQ637xE by future firmware updates.

User Interface

Enhanced user friendliness is achieved with the unit’s high-resolution, responsive 10.4-inch multi-touch capacitive LCD touchscreen, which makes operating the device even simpler and more intuitive.

Users can change measurement conditions, perform analysis and change the optical spectrum view as simply as operating a tablet device.

The AQ637xE’s screen design and intuitive operability is inherited from Yokogawa’s best-selling optical spectrum analyser. This proven interface has served the needs of many thousands of users around the world in areas such as R&D testing and manufacturing testing.

Usability is further improved by the addition of frequently used keys to the hardware keys on the front panel. These include keys for sweep control (Auto/Single/Repeat/Stop), resolution setting, and sensitivity setting.

The AQ637xE also features USB ports that are compatible with a USB storage device, mouse and keyboard. Data and screenshots can be saved to internal memory or USB storage to create test reports, while connecting a mouse or keyboard to the USB port allows the AQ637xE to be operated in the same way as a PC.

The standard LAN port allows convenient access to files stored in the internal memory as well as allowing remote firmware updates from a PC. The APP function also supports a fibre inspection probe, allowing users to visualise the quality of the fibre connector surface.

Jonathan Newell
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