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Yokogawa's new AQ6375B is an optical spectrum analyser operating in the short-wavelength infrared (SWIR) region covering wavelengths from 1200 to 2400 nm. With a design based on the company's AQ6375 instrument, the new analyser combines high measurement performance with ease of operation, and incorporates a number of new features including a gas purging feature, a built-in cut-off filter, data-logging capabilities, a double-speed mode, and support for Windows file sharing.

The AQ6375B offers high wavelength accuracy of ±0.05nm (1520 to 1580nm), ±0.50nm (full range) and high wavelength resolution of 0.05nm, a wide close-in dynamic range of 55dB, and a wide measurement level range from +20dBm to -70dBm. The use of an advanced monochromator design helps to separate spectral signals in close proximity to one another, and improves the dynamic range by reducing the influence of stray light.

In conjunction with new high-speed circuitry and noise reduction techniques, the monochromator also enables the AQ6375B to achieve a high measurement speed: up to 0.5 sec/100nm. The double-speed mode makes it possible to measure an optical signal in half the time compared with the conventional mode, with only a 2dB penalty over the standard sensitivity value.

A free-space optical input makes it possible to connect multimode and single-mode fibres on the same instrument. It also provides a low and stable insertion loss for multimode fibres, which helps to maintain the excellent measurement efficiency as well as increasing measurement repeatability. The lack of physical contact also eliminates the possibility of damage when fibres are connected.

The new purging feature is designed to minimise the influence of water-vapour absorption on spectral measurements carried out in the SWIR region. By continuously supplying a pure purge gas such as nitrogen to the monochromator through the dedicated connectors on the back panel, these absorption effects are significantly reduced.

Also new is the built-in cut-off filter for the high-order diffracted light generated by the monochromator at wavelengths equal to integral multiples of the input wavelength. By cutting incoming light below 1150nm with the built-in filter, the AQ6375B reduces the influence of secondary diffracted light on the measurement by 50dB or more at wavelengths up to about 2300nm. As a result, the measured data are always reliable and replicate the real signal under test.

A new data-logging function is available on the AQ6375B for recording analysis results such as distributed feedback laser diode (DFB-LD) analysis and multi-peak measurements at up to 10,000 points per channel with time stamps. Recorded data can be displayed in table and graphical formats. This function is useful for the long-term stability testing and temperature cycle testing of systems and devices. The optical spectrum of each measurement can also be stored for reviewing and troubleshooting.

For transferring acquired data for subsequent analysis, a Windows file sharing function is available in addition to the existing Ethernet/GPIB and USB interfaces. This uses Windows Explorer to access the user area of internal memory via the Ethernet interface using the Windows SMB (Server Message Block) function.

Applications for the AQ6375B cover the analysis of telecom devices and systems operating in single-mode transmission in all the windows of optical communications from the beginning of the O-band at 1260nm to the end of the U-band at 1675nm.

The AQ6375B is also suitable for measurements in other areas such as environmental monitoring – including the sensing of gases such as NOx and CO2 – atmospheric observation, and the medical and biomedical sector for virus sensing and checking surgical equipment. This includes manufacturers of optical devices in these sectors using the AQ6375B for both R&D and production testing.