Method and apparatus for measuring optical attenuation of an optical medium

An apparatus for implementing a method of measuring the optical attenuation of an optical medium, said apparatus comprising;

• means for performing a first measuring process by passing a first optical measuring signal through the optical medium in a first direction, including a first measuring transmitter coupled to a first end of the optical medium to couple in the first optical measuring signal and a first measuring receiver coupled to a second end of the optical medium for coupling the first optical measuring signal out and measuring the coupled out signal, means for performing a second measuring the coupled out signal, means for performing a second measuring process by passing a second optical measuring signal through the optical medium in a second opposite direction, including a second measuring transmitter coupled to the second end of the optical medium for coupling in a second optical measuring signal and a second measuring receiver coupled to the first end of said optical medium for coupling the second measured signal out and measuring the second coupled out signal, means for performing a third measuring process by transmitting the first signal from the first transmitter to the first receiver without passing the signal through the optical medium and measuring the first signal in the first measuring receiver;
• means for performing a fourth measuring process by transmitting the second measuring signal from the second transmitter to the second receiver without passing the second signal through the optical medium and measuring the second signal in the second measuring receiver and thereby obtaining four measured values from the four preceding means;
• means for then utilizing the four measured values for identifying the attenuation of the optical medium;
• and means for measuring a spatially extending optical medium including adding means for modulating the second signal of the second transmitter by a measured signal received by the first measuring receiver, means for transmitting the modulated signal of the second transmitter through the optical medium to the second receiver, and means for demodulating the modulating signal received by the second receiver;
• each of said receivers having bending couplers for forming the coupling to an optical waveguide.

An apparatus for implementing a method of measuring the optical attenuation of an optical medium, said apparatus comprising:

• means for performing a first measuring process by passing a first optical measuring signal through the optical medium in a first direction, including only a single measuring transmitter to couple in the first optical measuring signal to a first end of the optical medium and a single measuring receiver for coupling the first optical measuring signal out from a second end of the optical medium and measuring the first coupled out signal and means to selectively couple said single measuring transmitter and said single measuring receiver in an arrangement at opposite ends of the optical medium to make a first measurement, said means to selectively couple including bending couplers to form the coupling to the optical waveguide,
• means for performing a second measuring process by passing a second optical measuring signal through the optical medium in a second opposite direction, including said single measuring transmitter for coupling in a second optical measuring signal to the second end of the optical medium and said single measuring receiver for coupling out the second measured signal out from the first end of said optical medium and measuring the second coupled out signal and means to selectively couple said single measuring transmitter and said single measuring receiver in an arrangement at opposite ends of the optical medium to make a second measurement.
• means for performing a third measuring process by passing a said first optical measuring signal in said first direction directly from said single measuring transmitter to said single measuring receiver without passing said first measuring signal through the optical medium and measuring the first measuring signal in said single measuring receiver to make a third measurement,
• means for performing a fourth measuring process by passing a said second optical measuring signal in said second, opposite direction directly from said single measuring transmitter to said single measuring receiver without passing said second measuring signal through the optical medium and measuring the second measuring signal in said single measuring receiver to make a fourth measurement and thereby obtaining four measured values from the four preceding means;
• means for then utilizing the four measured values for identifying the attenuation of the optical medium.

A method for measuring optical attenuation of an optical medium comprising the steps of performing a first measuring process by coupling in a first optical measuring signal of a first optical transmitter to pass through the optical medium and coupling the signal out and measuring the signal in a first measuring receiver;

• performing a second measuring process by coupling a second optical measuring signal from a second optical transmitter to pass through the optical medium in the opposite direction and coupling out the second optical signal after passing through the optical medium and measuring this second optical signal in a second measuring receiver;
• performing a third measuring process by coupling in the first optical measuring signal and coupling it out without passing through the optical medium to be measured by the second measuring receiver;
• performing a fourth measuring process by coupling in the second optical measuring signal from the second optical transmitter and coupling it out without passing through the optical medium and measuring in the first measuring receiver and then utilizing the four measured values obtained by the four processes for identifying the attenuation of the optical medium, the optical frequency of the first optical transmitter and of the second optical transmitter being within a frequency band of interest for the transmission and the frequencies of the two optical signal of the two optical transmitters being selected to be different.