Flat triplet dual indoor optical cable using 900 μ M or 600 μ M flame retardant tightly buffered fiber optical transmission medium. Using a layer of tightly buffered fibers wrapped in aramid yarn as the strength component unit, and adding a layer of spiral steel wire; The unit is extruded with a layer of PVC or LSZH material as the inner jacket. Then use a layer of PVC or LSZH (low smoke, zero halogen, flame retardant) interlayer as the outer sheath to complete the optical cable.