YOKOGAWA AQ6377 Optical Spectrum Analyzer
Lasers are commonly used for the detection of gases such as CO2, N2O and NO in environmental monitoring. This detection is achieved by identifying the wavelength absorption lines of the different gases. Howeve the “side modes” of the laser, which are difficult to detect, reduce the laser’s ability to distinguish between the different gases.
This Yokogawa AQ6377 Optical Spectrum Analyzer has been designed to overcome this difficulty in the wavelength range from 3.5 to 5 µm (mid-infrared). It has a wavelength resolution of 0.2 nm, a wavelength accuracy of ±0.5 nm, a dynamic range of up to 50 dB and a level sensitivity of up to -60 dBm.
Quantum cascade lasers (QCLs), used in particular for medical spectroscopy diagnostics, operate using a pulsed technique. The AQ6377 analyzer is capable of making measurements over the entire wavelength range and evaluating pulsed QCL signals with a low repetition rate.
Improvement in dynamic range and sensitivity has been achieved by reducing the influence of stray light in the monochromator. The integrated calibration light source takes advantage of the natural absorption properties of acetylene gas to provide a wavelength calibration signal at 0.6 picometer precision. This source also has automatic optical alignment to compensate for any drift in the optical axis caused by vibrations and shocks during transport, as well as drift due to temperature changes.
In addition, the free space optical input allows both single-mode and multi-mode MWIR fibers (up to 400 µm) to be connected to the same optical spectrum analyzer, and ensures low insertion loss. The absence of physical contact also avoids the risk of damage when the fibers are connected.
Spectral measurements can be strongly affected by the absorption of water vapor and carbon dioxide. The purge function of the AQ6377 is designed to significantly reduce the influence of these gases by continuously supplying pure purge gas (such as nitrogen) to the monochromator via dedicated connectors on the rear panel.
- Wavelength range: 1900 to 5500 nm
- 5 wavelength resolution settings: 0.2 to 5 nm
Enables the user to choose the best value according to the device/system under test.
- Wide measurable level range: −60 to +13 dBm
Suitable to measure high power as well as low power sources used in different fields of application. Sensitivity: HIGH1-3 are only high dynamic mode.
- Wavelength accuracy: ±0.5 nm
Easily maintained due to the built-in Calibration Function and wavelength reference source.
- Close-in dynamic range: 50 dB
- Horizontal scale also in Wave Number (cm−1)
In addition to the commonly-used scales in wavelength (nm) and frequency (THz).
Due to the high resolution and sensitivity of the AQ6377, it can actually detect the presence of water molecules in the air. The water vapor is detected in the upper Near-IR wavelength region and could overlap with or mask the spectral characteristics of the actual device under test in that particular region.
By continuously supplying a pure purge gas such as nitrogen to the monochromator through the ports on the back panel, the AQ6377 can reduce the influence of water vapor absorptions and provide more reliable and accurate measurements than ever before.
Built-in Cut Filter for High Order Diffracted Light
Due to the diffractive technology used, the monochromator in some circumstances could generate high order diffracted light, which appears at wavelengths equal to the integral multiple of input wavelengths.
By cutting incoming light below 1500 nm with the built-in filter, the AQ6377 drastically reduces the influence of high order diffracted light on the measurement. Thus, the measured data are always reliable and replicate the real signal under test.
Double Speed Mode
Increases the sweep speed up to 2 times compared to the standard sweep mode, with only a 2 dB penalty to the standard sensitivity value.
Free-Space Optical Input
The AQ6377 uses a free-space optical input structure (i.e. no fiber is mounted inside the instrument), most effective for guaranteeing high coupling efficiency, measurement repeatability, and no maintenance.
This smart solution is:
- WORRY-FREE: no internal fiber can be scratched or get dirty by inaccurate coupling of fibers
- MAINTENANCE-FREE: no internal fiber has to be cleaned
- VERSATILE: the instrument accepts both /PC and /APC connectors
- DUAL PURPOSE: the instrument accepts both Single-Mode and Multi-Mode fibers without being affected by the high insertion loss from MM-SM fibers matching