English to German Tech/Engineering Patents Diodenlaserabsorptionsspektroskopie

As shown in Fig. 8, the current invention alleviates the problem of multiplexing and pitching light in a single
mode beam from 670 nm or 760 nm to 1.67 microns by utilizing a very short transmission section of multimode fiber
120 that does not allow the higher order spatial modes for a wavelength shorter than the single mode cutoff to develop.
Referring to equation 2 above, if the length, L, of multi-mode fiber is short, then mode noise will be minimized. In this
case, for example, if 760 nm light is coupled to a short section of single mode fiber with a cutoff wavelength of 1280 nm (e.g. Corning SMF 28), the 760 nm light remains single-mode for at least a few meters. Therefore a solution to pitch
side mode noise is to couple the 760 nm light into a fiber which is single mode for wavelengths longer than 1280 nm but
could be multimode for 760 nm, with only a short distance to go before it is collimated to be transmitted through the
measurement zone.