A routine of controlling the dilution cycle of an absorption chiller to determine when to initiate a dilution cycle, continue the cycle and terminate the cycle. This optical receiver includes a digital feedback circuit that biases a front-end circuit, which receives an optical signal, so that an analog electrical signal output by the front-end circuit is calibrated relative to a reference voltage corresponding to a decision threshold of a digital slicer in the optical receiver. The second cam phase change mechanism is set to have a variable-phase angular range wider than that of the first cam phase change mechanism. Within the mixer block, the single conductive path may be fanned out to at least two unit cells of the mixer block.