Contrary to , , and , can not be visualized as the difference (or interference) of two synthesized beams. However, it should still be regarded as a Sagnac combination since there exists a time-delay relationship between it and , , and :Symmetrized Sagnac combination.
By using the four generators, it is possible to construct several other interferometric combinations, such as the unequal-arm Michelson , the Beacons , the Monitors , and the Relays . Contrary to the Sagnac combinations, these only use four of the six data combinations , . For this reason they have obvious utility in the event of selected subsystem failures .
These observables can be written in terms of the Sagnac observables in the following way,In the case of the combination , in particular, by writing it in the following form ,  and ) that this combination can be visualized as the difference of two sums of phase measurements, each corresponding to a specific light path from a laser onboard spacecraft 1 having phase noise . The first square-bracket term in Equation (45) represents a synthesized light-beam transmitted from spacecraft 1 and made to bounce once at spacecraft 2 and 3, respectively. The second square-bracket term instead corresponds to another beam also originating from the same laser, experiencing the same overall delay as the first beam, but bouncing off spacecraft 3 first and then spacecraft 2. When they are recombined they will cancel the laser phase fluctuations exactly, having both experienced the same total delay (assuming stationary spacecraft). The combinations should therefore be regarded as the response of a zero-area Sagnac interferometer.
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