Test & measurement
Tenerife and at the Aristarchos 2.2 m telescope at the Chelmos observatory in the Peloponnese in Greece. Maintaining the exact transmitter
wavelength is a critical part of the Aristarchos system’s operation, achieved by a technique where the transmitter laser is pumped by an 808nm laser diode to generate an accurate 1,064.625nm ±11 pm output. This wavelength is controlled accurately by adjusting the operating temperature of the transmitter laser. Measurement of optical communications
systems is usually performed using an optical spectrum analyser (OSA), a highly accurate and reliable instrument that analyses optical wavelength, among other criteria. OSAs such as Yokogawa’s AQ6370D
achieve a wavelength measurement accuracy of ±10pm (picometres) at a reference wavelength of 1,550nm and ±100pm at 1,064.625nm. Although this is highly accurate, it is still not accurate enough to meet the demands of the Aristarchos installation. Zoran Sodnik is the optical
communications technology manager at the ESA’s telecommunications and integrated
Instrumentation Monthly February 2022
applications directorate. He is responsible for the optical communications system installed with the Aristarchos telescope. Sodnik says: “The EDRS operates at frequencies measured in multiples of terahertz and the transmitter and receiver wavelengths are no more than 28 Gigahertz apart. This means that the laser’s frequency has to be set with Gigahertz precision, and then measured with the same level of precision and accuracy.” Working with Simac Electronics, a
Netherlands-based supplier of connectivity and measurement technologies, the ESA selected a specialist optical wavelength meter, the AQ6151B from Yokogawa. The instrument uses a Michelson
interferometer, capable of measuring wavelength very accurately. In the AQ6151B, the high accuracy model in the AQ6150 Series, accuracy is specified at ±0.2 ppm. Available in three wavelength ranges, the Aristarchos installation uses the Wide Range version, covering wavelengths from 900nm to 1,700 nm. The AQ6150 series offers high speed, with
the ability to acquire, analyse and transfer a measurement to a PC within 0.2 seconds.
As well as high accuracy, the AQ6150 Series offers simultaneous measurement of up to 1,024 wavelengths and handles input signal power as low as -40 dBm. The AQ6151B also has built-in analysis
functions and requires no programming, making it easy to use. Sodnik was confident that using the
Yokogawa optical wavelength meter would produce the results that the ESA was looking for: “The ESA has used Yokogawa instruments extensively in the past and has always found them to be extremely accurate and reliable. This latest installation at the Chelmos observatory called for extremely high accuracy. I had no hesitation in selecting a Yokogawa product – it has fully lived up to my expectations.” Using the highly accurate AQ6151B to tune
lasers, ESA expects that optical transmission could take on the burden of handling high bandwidth traffic, replacing radio communication as the primary means of sending and receiving data from satellites.
Yokogawa Test & Measurement
tmi.yokogawa.com
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