An optical encoder includes first, second, and third light receiving elements (A, B, C) that are sequentially disposed and adjacent to each other; and a detection signal generation unit (50) that outputs a detection trigger (Ts) when an output level of the second light receiving element (B) that receives incident light after the first light receiving element (A) is higher than an output level of the first light receiving element A, and outputs a non-detection trigger (Te) when an output level of the third light receiving element (C) that receives incident light after the second light receiving element (B) is higher than the output level of the second light receiving element (B).

A method of determining a direction of rotation of a shaft is disclosed, as well as an integrated circuit chip that uses the disclosed method. The method includes receiving a first binary signal and a second binary signal from a transducer attached to the shaft, with the first and second binary signals being in quadrature. A present quadrant identification number, QID.sub.PRESENT, is determined as a two-digit binary number by left-shifting a value of the first signal and adding a value of the second signal. After a sampling interval has elapsed, the method sets a past quadrant identification number, QID.sub.PAST, to the value of said QID.sub.PRESENT, determines a new value of QID.sub.PRESENT and calculates a value of a transition code using an equation that operates on QID.sub.PRESENT and QID.sub.PAST. The method uses the transition code to determine a direction of rotation of the shaft.

To reduce costs by adopting a direct modulation system in which a semiconductor laser is directly modulated. An optical fiber sensor includes a light source configured to generate an optical pulse as probe light by a direct modulation system, an optical bandpass filter configured to extract anti-Stokes light that is a component on an anti-Stokes side of Brillouin scattered light from backscattered light generated by the probe light in an optical fiber to be measured, an interference signal acquisition unit configured to generate an interference signal by self-delayed heterodyne interference from the anti-Stokes light extracted at the optical bandpass filter and input to the interference signal acquisition unit and a Brillouin frequency shift acquisition unit configured to acquire a Brillouin frequency shift amount from the interference signal.

A method of determining a direction of rotation of a shaft is disclosed, as well as an integrated circuit chip that uses the disclosed method. The method includes receiving a first binary signal and a second binary signal from a transducer attached to the shaft, with the first and second binary signals being in quadrature. A present quadrant identification number, QID.sub.PRESENT, is determined as a two-digit binary number by left-shifting a value of the first signal and adding a value of the second signal. After a sampling interval has elapsed, the method sets a past quadrant identification number, QID.sub.PAST, to the value of said QID.sub.PRESENT, determines a new value of QID.sub.PRESENT and calculates a value of a transition code using an equation that operates on QID.sub.PRESENT and QID.sub.PAST. The method uses the transition code to determine a direction of rotation of the shaft.

A method of determining a direction of rotation of a shaft is disclosed, as well as an integrated circuit chip that uses the disclosed method. The method includes receiving a first binary signal and a second binary signal from a transducer attached to the shaft, with the first and second binary signals being in quadrature. A present quadrant identification number, QID.sub.PRESENT, is determined as a two-digit binary number by left-shifting a value of the first signal and adding a value of the second signal. After a sampling interval has elapsed, the method sets a past quadrant identification number, QID.sub.PAST, to the value of said QID.sub.PRESENT, determines a new value of QID.sub.PRESENT and calculates a value of a transition code using an equation that operates on QID.sub.PRESENT and QID.sub.PAST. The method uses the transition code to determine a direction of rotation of the shaft.

A method of determining a direction of rotation of a shaft is disclosed, as well as an integrated circuit chip that uses the disclosed method. The method includes receiving a first binary signal and a second binary signal from a transducer attached to the shaft, with the first and second binary signals being in quadrature. A present quadrant identification number, QID.sub.PRESENT, is determined as a two-digit binary number by left-shifting a value of the first signal and adding a value of the second signal. After a sampling interval has elapsed, the method sets a past quadrant identification number, QID.sub.PAST, to the value of said QID.sub.PRESENT, determines a new value of QID.sub.PRESENT and calculates a value of a transition code using an equation that operates on QID.sub.PRESENT and QID.sub.PAST. The method uses the transition code to determine a direction of rotation of the shaft.

To reduce costs by adopting a direct modulation system in which a semiconductor laser is directly modulated. An optical fiber sensor includes a light source configured to generate an optical pulse as probe light by a direct modulation system, an optical bandpass filter configured to extract anti-Stokes light that is a component on an anti-Stokes side of Brillouin scattered light from backscattered light generated by the probe light in an optical fiber to be measured, an interference signal acquisition unit configured to generate an interference signal by self-delayed heterodyne interference from the anti-Stokes light extracted at the optical bandpass filter and input to the interference signal acquisition unit and a Brillouin frequency shift acquisition unit configured to acquire a Brillouin frequency shift amount from the interference signal.

An optical encoder includes first, second, and third light receiving elements (A, B, C) that are sequentially disposed and adjacent to each other; and a detection signal generation unit (50) that outputs a detection trigger (Ts) when an output level of the second light receiving element (B) that receives incident light after the first light receiving element (A) is higher than an output level of the first light receiving element A, and outputs a non-detection trigger (Te) when an output level of the third light receiving element (C) that receives incident light after the second light receiving element (B) is higher than the output level of the second light receiving element (B).