- Yokogawa introduces broadband optical spectrum analyzer which opens new opportunities for environmental sensing and medical applications
- Its AQ6377 optical spectrum analyzer, which covers a wavelength range from 1900 to 5500 nm, is characterized by its ability to analyze the side modes of mid-wave infrared (MWIR) lasers as well as the pulsed signals of quantum cascade lasers (QCL).
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. However, according to Yokogawa, the “side modes” of the laser, which are difficult to detect, reduce the laser’s ability to distinguish between the different gases.
His new optical spectrum analyzer AQ6377 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.
# Main features of the AQ6377 analyzer :
- Wavelength range: 1900 to 5500 nm
- Resolution: 0.2 to 5 nm
- Wavelength accuracy: ±0.5 nm
- Level range: -60 to +13 dBm
- Dynamic range: 50 dB