The Supercontinuum Fiber Laser as a Key Component in the Characterization of Ratiometric Instruments

Characterizing an optical system is a critical process that underpins the development, optimization, and deployment of optical technologies. This process involves a comprehensive analysis and measurement of the system’s properties and performance. This procedure includes determining key parameters such as optical efficiency, wavelength range, resolution, sensitivity, signal-to-noise ratio, and other specific attributes depending on the system’s application. The characterization process involves experimental testing, data acquisition, and analysis to fully understand how the optical system behaves under various conditions and inputs. 

By thoroughly understanding the system’s performance through detailed measurements and analysis, designers and engineers can ensure that the system operates effectively and meets the required specifications for its intended application. This process not only enhances the system’s reliability and efficiency but also fosters innovation and continuous improvement in the field of optics. Through this process, the optical system can achieve its full potential, providing precise, reliable, and high-quality performance. 

In the characterization process, a Supercontinuum Laser could be a great component of the setup due to its broadband, high brightness and high-power stability. One good example of this is the article “Highly Coupled Seven-Core Fiber for Ratiometric Anti-Phase Sensing” where Natanael Cuando-Espitia from the CONACyT-Electronics Department at Universidad de Guanajuato show us the process of design and experimentally test a ratiometric sensor including its characterization process using a supercontinium laser. 

 Experimental setup 

The experiment was designed to measure the variation between the phases of two paths of Highly Coupled Seven-Core Fiber in a range of temperatures from 25ºC to 400ºC. These paths were made of an initial and final part of single-mode fibers (SMF) and a middle part of seven-core highly coupled fiber (SCF) resulting in a device with a disposition SMF-SCF-SMF. The setup also counts with a Supercontinuum laser (used for characterization), an LD operating at 1550 nm (used in the implementation) and a station of detection formed for an optical spectrum analyzer, a 100 MHz oscilloscope and two photodetectors. 


Figure 1 - Experimental setup [1].
Figure 1 – Experimental setup [1].


To establish the baseline response the researchers connected the supercontinuum laser to both paths and sensed the phases, to make them meet at half of the intensity range (this operation point was chosen because of the high linearity of the sin function around this point) they must curve the path D1 until its function of intensity match the desired shape (Figure 2 a). Whit the second path (D2) this curvature was unnecessary and remains straight (Figure 2 b). 

Figure 2 - Experimental results of spectral characterization [1].
Figure 2 – Experimental results of spectral characterization [1].

This part of the process reveals the principal advantages of using a Supercontinuum Laser Iceblink in the characterization of optical systems: 

  • Its broadband from 450 to 2300 nm allowed for the detailed examination of the SCF’s (Seven-Core Fiber) spectral response. This broad range was necessary to capture the entire spectral shift and ensure accurate measurement of the anti-phase behavior. 
  • High-power stability with variations of < 0.5% (std. dev.) minimizes the source variation in the intensity making the intensity function as reliable as possible. 
  • The high brightness ensured that sufficient light intensity was available across the spectrum, leading to clear and precise spectral data. This was particularly important for detecting subtle changes in the spectral characteristics of the SCF. 

To finalize the characterization process, the temperature of both paths was raced from 25ºC to 400ºC in intervals of 25 ºC to see the variation in the intensity function and determine the correlation between this function and the variation of temperature (Figure 2 c) 

As we can see, characterization was essential to understanding the interferometric-like behaviour and temperature-induced spectral shifts of the SCF. For this kind of application where the precision in the measurement is the main objective, having a reliable light source for your setup characterization is the key to success.