Wavelength division multiplexing (WDM) is a promising solution for upgrading the capacity of polymer optical fiber (POF)-based telecommunication networks. In this letter, we report on the successful realization of a four-channel highspeed WDM transmission system for 1-mm diameter step-index POF (SI-POF). For combining the optical signals coming from 405-, 450-, 515-, and 639-nm laser diodes onto 1-mm SI-POF, a 4 × 1 coupler with low insertion loss (IL) has been developed. To spatially separate different wavelength channels, a fourchannel demultiplexer with low IL (<5.7 dB) and high (non)adjacent channel isolation (>30 dB) has been realized in bulk optics. The 14.77-Gb/s data transmission based on the offline-processed discrete multitone modulation technique has been demonstrated over 50-m SI-POF at a bit-error rate of 10 −3 .Index Terms-Demultiplexer, optical interconnections, optical fiber communication, polymer optical fiber, visible diode lasers, wavelength division multiplexing.
Using a tetrahedral tip as a probe, it is possible to combine the techniques of scanning tunneling microscopy (STM) and scanning near-field optical microscopy (SNOM) in the same probe tip so that the probing of the respective near-field interactions occurs virtually at the same spot of the tip. Atomic resolution on pyrolytic graphite and stable images on rough samples are routinely obtained in the STM mode. In the combined SNOM/STM mode, an absorption contrast in the optical image is obtained with images of evaporated silver films on glass as well as of silver deposited on an indium tin oxide substrate. We obtained a point-to-point resolution of 6 nm, whereas the edge resolution is about 1 nm.
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