Aragon Photonics is a developer and manufacturer of innovative all-optical solutions for high resolution measurements. Its signature product is the BOSA, which it says is the highest resolution optical spectrum analyser (OSA) on the market. According to Aragon, the hard specified 10-MHz (0.08-pm) resolution and simultaneous dynamic range of 80 dB of the BOSA can only be achieved by making use of its patent-pending all-optical technology. The traditional heterodyne and interferometric methods for optical spectrum analysis are based on optically combining a tunable laser signal (TLS) with the signal-under-test (SUT) and electrically processing the photodetected spectrum. However, there is a trade-off among the attributes of resolution, dynamic range and wavelength range. In addition, there is an inherent limitation due to the sidemodes of the TLS. These sidemodes become part of the measurement result and are indistinguishable from the characteristics of the SUT by causing spurious (false) signals. On the other hand, the BOSA technology, utilizing stimulated Brillouin scattering, relies on a pure optical analysis of the SUT transmitted through a nonlinear medium stimulated by a counter-propagating probe laser (TLS). This process creates the equivalent of an optical filter with 3-dB and 60-dB bandwidths of 0.08 pm and 0.44 pm, respectively, and is valid for any wavelength span. The counter-propagation provides immunity to TLS sidemodes.