The LNFR-100 OPT D is an ultra-low noise 5 MHz, 10 MHz and 100 MHz source. The instrument can be used as a low noise frequency reference for time frequency and quantum applications. It can also be used as a cleanup oscillator for optically stabilized sources. The LNFR-100 OPT D contains a 10 MHz and a 100 MHz ultra low noise ovenized oscillator. The internal 100 MHz oscillator is distributed to provide two outputs at 100 MHz. The two outputs at 5 MHz and 10 MHz are obtained by dividing the 100 MHz signal. The 100 MHz oscillator can be locked to an internal 10 MHz low noise oscillator for standalone operation or it can be locked to an external 100 MHz reference, using a switch on the front panel. The instrument is available in a 1U, 19-inch rackmount enclosure, and the instrument runs on AC or DC power. The instrument has monitoring LEDs for the power sources, internal oscillator status, reference lock status, and the external reference.