For systems based on array source, owing to discrete single sources in the array, variation in power intensity can usually be detected as the receiving end moves. Although uniform illumination in lighting system has been widely investigated, its implemented light sources are commonly LEDs with Lambertian distribution. We further study an optical design applied for optical wireless communication system with VCSEL in this article. The optical system mainly consists of collimating lens and micro lens array to homogenize power intensity of the communication system based on VCSEL array source which has a Gaussian distribution. Our proposed scheme was verified with commercial optical design software Zemax. The simulation result shows that illumination uniformity can reach up to 91% after passing through this optical system, which can fulfill the requirements of high power uniformity in practical applications. The homogenization of power intensity solves the issue of signal power variation at the moving receiver end in optical wireless communication system, which guarantees stable communication link and robust system performance.
Collimation is important for long-range transmission in a Wireless Optical Communication (WOC) system. We developed a novel method to control the size of lens used in collimation of VCSEL based WOC systems. In our design example, the divergence angle is well-controlled to be 0.106 mrad achieved by two lenses with each focal length > 60mm and the system total length < 80 mm. Also, we proposed a universal framework based on light field representation for modeling similar optical systems.
A packaged microbubble resonator with an outer diameter of 210 μm and wall thickness around 3 Μm has been fabricated which can achieve a sensitivity of 71 nm/RIU for refractive index measurement. We further propose it for laser wavelength monitoring with excellent performance verified for both low and high power laser inputs. Combined with the self-referenced differential-mode technique, we can measure the laser wavelength drift of 0.35 pm at low power level and 0.07 pm at high power level, respectively.