An elevator system comprising: an elevator car; a counterweight; a sheave assembly having a suspension sheave portion and a compensation sheave portion that guides the elevator car on a car side of the sheave assembly and guides the counterweight on a counterweight side of the sheave assembly; a suspension rope passing over and guided by the suspension sheave portion, the suspension rope having a first suspension end coupled to the elevator car on the car side and a second suspension end coupled to the counterweight on the counterweight side; a first compensation rope passing around the compensation sheave portion, the first compensation rope having a first compensation end coupled to the elevator car on the car side and a second compensation end coupled to the counterweight on the counterweight side; a first optical sensor assembly having a first optical sensor pair including a first emitter (220A1) and a first receiver (220A2), the first emitter (220A1) configured to emit a first beam to be received by the first receiver (220A2), the first optical sensor pair configured to detect interruption of the first beam by the first compensation rope; wherein the first optical sensor assembly further comprises: a second optical sensor pair including a second emitter (220B1) and a second receiver (220B2), the second emitter (220B1) configured to emit a second beam to be received by the second receiver (220B2), the second optical sensor pair configured to detect interruption of the second beam by the second compensation rope and a controller that controls movement of the elevator car based on the detected interruption characterized in that the elevator system further comprises: a second compensation rope passing around the compensation sheave portion, wherein the second optical sensor pair is configured to detect interruption of the second beam by the second compensation rope and wherein the first optical sensor pair and second optical sensor pair are arranged to each detect interruption upon movement of the first and second compensation ropes (24A, 24B) toward each other. an elevator car; a counterweight; a sheave assembly having a suspension sheave portion and a compensation sheave portion that guides the elevator car on a car side of the sheave assembly and guides the counterweight on a counterweight side of the sheave assembly; a suspension rope passing over and guided by the suspension sheave portion, the suspension rope having a first suspension end coupled to the elevator car on the car side and a second suspension end coupled to the counterweight on the counterweight side; a first compensation rope passing around the compensation sheave portion, the first compensation rope having a first compensation end coupled to the elevator car on the car side and a second compensation end coupled to the counterweight on the counterweight side; a first optical sensor assembly having a first optical sensor pair including a first emitter (220A1) and a first receiver (220A2), the first emitter (220A1) configured to emit a first beam to be received by the first receiver (220A2), the first optical sensor pair configured to detect interruption of the first beam by the first compensation rope; wherein the first optical sensor assembly further comprises: a second optical sensor pair including a second emitter (220B1) and a second receiver (220B2), the second emitter (220B1) configured to emit a second beam to be received by the second receiver (220B2), the second optical sensor pair configured to detect interruption of the second beam by the second compensation rope and a controller that controls movement of the elevator car based on the detected interruption a second optical sensor pair including a second emitter (220B1) and a second receiver (220B2), the second emitter (220B1) configured to emit a second beam to be received by the second receiver (220B2), the second optical sensor pair configured to detect interruption of the second beam by the second compensation rope and a controller that controls movement of the elevator car based on the detected interruption characterized in that the elevator system further comprises: a second compensation rope passing around the compensation sheave portion, wherein the second optical sensor pair is configured to detect interruption of the second beam by the second compensation rope and wherein the first optical sensor pair and second optical sensor pair are arranged to each detect interruption upon movement of the first and second compensation ropes (24A, 24B) toward each other. a second compensation rope passing around the compensation sheave portion, wherein the second optical sensor pair is configured to detect interruption of the second beam by the second compensation rope and wherein the first optical sensor pair and second optical sensor pair are arranged to each detect interruption upon movement of the first and second compensation ropes (24A, 24B) toward each other.