Abstract: An OTDR stores data samples in a predetermined sequence in a memory. Data is read from and written to the memory in the predetermined sequence by application of successive control signals. The stored data is read, added to a correlated sample of a new signal and the result stored to maintain the predetermined sequence of samples. Successive tests thus accumulate samples in sequence to provide an indication of the variation of the signal as the light pulse passes along the fiber under tests.

Abstract: An OTDR to examine light reflected from an optic fibre has an amplification stage that operates in either a high gain or low gain mode. To avoid saturation of the amplifier in the high gain mode, the trace is examined to identify the location of spikes and a switch is controlled to connect the amplifier to the signal after the occurrence of the spike.

Abstract: A method for identifying optical features along the length of a fiber optic cable in response to injecting a pulse of light into the fiber optic cable and collecting data corresponding to signals which are reflected, the method comprising the steps of: identifying potential optical features in the data according to a first set of parameters; constructing a pattern for selecting optical features from said potential optical features; fitting said pattern to said optical features; determining a position along the cable for each of said optical features; and computing a reflectance/loss level for each of said optical features.

Abstract: A digitizer suitable for digitizing input signals having a high dynamic range. The digitizer is microprocessor controlled and comprises an input stage, a multi-channel attenuator or amplifier bank, a multiplexer and a analog-to-digital (A/D) converter. The function of the multi-channel bank is to move the input signal within the range of the A/D converter. The input signal to be digitized is fed through the input stage to each of the channels in the attenuator bank. The signal is scaled by each respective channel in the attenuator bank. The multiplexer is used to switch the scaled signal which is within the range of the A/D converter for digitizing. The digitized sample is then corrected according to the attenuation or gain factor of the scaled channel. The digitizer includes a comparator bank which is used to determine the channel with the widest signal range within the range of the A/D converter. The digitizer also includes a channel calibrator for calibrating the actual gain or attenuation of each channel.

Abstract: A switched boxcar integrating circuit suitable for use with high speed data acquisition systems such as an Optical Domain Reflectometer. The boxcar integrator comprises a differential pre-amplifier stage, a sampling switch, and an integrator. The sampling switch couples the output of the pre-amplifier to the input of the integrator. The integrator includes non-inverting and inverting stages for producing a differential integrated signal. The switch samples the output of the pre-amplifier. The samples are integrated by the integrator once a sufficient number have been acquired. The sampling switch includes a switch controller to synchronize the operation of the switch with the received signals. The integrator also includes an offset compensator and a reset switch which are coupled to the integrator. The offset compensator and reset switch set the integrator to zero and also correct any offset error.