An apparatus comprises a robotic manipulator and a surgical instrument mounted to the robotic manipulator. The surgical instrument comprises an elongate arm including an actively controlled bendable region including at least one joint region and an end effector and a passively bendable region including a distal end coupled to the actively controlled bendable region. An actuation mechanism extends through the passively bendable region and is coupled to the at least one joint region to control the actively controlled bendable region. A channel extends through the elongate arm, and an optical fiber is positioned in the channel. The optical fiber includes an optical fiber bend sensor in at least one of the passively bendable region or the actively controlled bendable region.