We demonstrate for the first time a near shot noise limited in-line Sagnac interferometer current sensor. It is shown to have a number of advantages over the optical current sensors based on polarimetric Faraday and Faraday/Sagnac loop interferometer topologies, including lower sensitivity to environmental disturbances, less demanding optical components, and easy installation. Our contributions to the field of fiber-optic current sensors include the demonstration of a near shot noise limited in-line Sagnac interferometer current sensor and a demonstration of the effects of the acoustic and thermal perturbations on our sensor. In addition, a new high power ($>$1-mW fiber pigtailed) broadband source using coherence-collapsed 1.3 $\mu$m multimode laser diode was investigated. We believe that this source is an attractive low-cost alternative to edge light emitting, superluminescent diode, and fiber light source. Furthermore, we examine the limit of a noise subtraction technique in our Sagnac interferometer current sensor.