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Problems and solutions for the far end measurement of frequency characteristics of the baseband response of a multimode fiber due to dispersion are presented. Also described is a configuration of the measuring equipment of the baseband response. For the latter, the following are important: (i) removal of the effect of the material dispersion; (ii) stabilization and leveling of the modulation level; (iii) stabilization of the optical output level; (iv) removal of the effect of the reflected light from the output end and the input end of the fiber. Solutions for these problems are: (i) single-mode oscillation of the semiconductor laser by reduction of the modulation index; (ii) stabilization and leveling of the modulation level by a negative feedback loop that monitors the modulation level of the backward light of the laser; (iii) stabilization of the optical output by a negative feedback loop that monitors the output level of the backward light of the laser; and (iv) removal of the effect of the reflected light by means of oblique incidence and small input aperture angle. When the baseband characteristic of a fiber a few kilometers long is measured, irregular variations are observed. A solution to this problem is also included. [ABSTRACT FROM AUTHOR]

A new optical wavemeter using a quartz azimuth rotator for direct reading of wavelength is described. When linearly polarized light having a certain wavelength enters the quartz rotator the plane of polarization rotates, the angle of rotation depending on the thickness of the quartz and the wavelength. Since the thickness of the quartz in the wavemeter is kept constant, the wave- length can be read from the angle of rotation of the polarized input light. This angle is obtained from the ratio of two polarized light beams which are divided from the input light by using an optical analyzer. The quartz thickness at which the error in measurement of wavelength is minimum is found. The relationship between the dividing ratio of the beams and the wavelength is also found. An azimuth quartz rotator with optimum thick- ness is fabricated. It is confirmed that the calculated and measured characteristics of the dividing ratio versus wavelength are in good agreement. The wavemeter has a wave- length range of 0.6–1.6 μm and measurement accuracy better than 1 nm at input power of -35 dBm. To increase the utility of the wavemeter, a device to measure its input power with high sensitivity is added to the apparatus, the resulting accuracy being better than 0.1 dB at an input level of -35 dBm. [ABSTRACT FROM AUTHOR]

The degree of pore filling is an important parameter for defining guest@MOF properties in applications including electronics, optics, and gas separation. However, the interplay of key aspects of host–guest interactions, such as a quantitative description of the guest alignment or the structural integrity of the host as function of pore filling are yet to be determined. Polarisation‐dependent infrared spectroscopy in attenuated total reflection configuration combined with gas sorption allowed to simultaneously study the orientation of the guest molecule and structural changes of the MOF framework during the pore filling process. Thereby we found, that initially randomly oriented guest molecules align with increasing pore filling during adsorption from the gas phase. At the same time, the framework itself undergoes a reversible, guest molecule‐dependent rotation of the aromatic linker and a linker detachment process, which induce defects. [ABSTRACT FROM AUTHOR]