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Miniature bulk optics for best transfer of modal distribution Built-in power monitoring for accurate power setting and stabilizing Wavelength range: 800 – 1370 nm Relative power monitor uncertainty: ±0.1 dB ± 300 pW Settling time: typ. 200 ms Transition speed: selectable from 0.1 to 80 and 1000 dB/s Optical path blocking: typ. >60 dB Optical attenuator instruments are used to flexibly control optical signal power levels in test setups. A primary application is determining optical receiver sensitivity by measuring the BER vs. input signal power. The N7768C provides 4 attenuator channels for 50 µm/ OM3 multimode fiber setups.  For dependable multimode transceiver testing, the instrument used to set the power level should not change this modal distribution. The bulk-optic filter and collimated beam path of the N7768C multimode attenuator is designed to assure homogeneous attenuation of all input modes. It maintains the beam profile of signals that comply with the encircled flux conditions of IEC 61280-4-1. The output power is monitored, especially to allow accurate and stable power setting independent of the input power. Convenient offset parameters allow the set power to correspond to the signal after other optical components in the setup path.