1. A low insertion loss optical coherence tomography system with space-division multiplexing, the system comprising: a long coherence light source producing coherent light having a coherence length greater than 5 mm to provide optimal imaging depth; an optical coupler receiving and dividing the light into reference light and sampling light; a reference arm defining a first optical light path, the reference arm receiving the reference light and generating a reference light signal based on the reference light; a sample arm defining a second optical light path and receiving the sampling light; an optical splitter arranged on the sample arm, the optical splitter dividing the sampling light into a plurality of sampling light beams and simultaneously transmitting the plurality of sampling beams; an optical delay element comprising a plurality of different light path lengths configured and operable to produce an optical delay shorter than the coherence length of the light source between the plurality of sampling beams such that when images are formed, signals from different physical locations are detected in different frequency bands; a scanner arranged to receive and configured to simultaneously scan the plurality of sampling beams simultaneously onto multiple different sampling locations on a surface of a sample; a plurality of optical couplers each configured and arranged to simultaneously receive and combine the reference light signal with one of a plurality of individual reflected light signals returned from the multiple different sampling locations on the surface of the sample produced by each of the plurality of sampling beams to simultaneously generate a plurality of interference signals each having a different frequency band; and a sensor configured to detect and combine the plurality of interference signals; wherein the interference signals includes data representing digitized images of the sample.