  In this work, we describe an updated version of single arm locking, and the
noise amplification due to the nulls can be flexibly restricted with the help
of optical frequency comb. We show that, the laser phase noise can be divided
by a specific factor with optical frequency comb as the bridge. The analytical
results indicate that, the peaks in the science band have been greatly reduced.
The performance of the noise suppression shows that the total noise after arm
locking can well satisfy the requirement of time delay interferometry, even
with the free-running laser source. We also estimate the frequency pulling
characteristics of the updated single arm locking, and the results suggest that
the pulling rate can be tolerated, without the risk of mode hopping. Arm
locking will be a valuable solution for the noise reduction in the space-borne
GW detectors. We demonstrate that, with the precise control of the returned
laser phase noise, the noise amplification in the science band can be
efficiently suppressed based on the updated single arm locking. Not only our
method allows the suppression of the peaks, the high gain, low pulling rate, it
can also serve for full year, without the potential risk of locking failure due
to the arm length mismatch. We finally discuss the unified demonstration of the
updated single arm locking, where both the local and the returned laser phase
noises can be tuned to generate the expected arm-locking sensor actually. Our
work could provide a powerful method for the arm locking in the future
space-borne GW detectors.
