An ultrastable PLL mode-locked fiber laser with a hydrogen maser clock

Ultrahigh-speed fiber laser and its application to optical metrology

“…2(d), the timing jitter is estimated to be as little as 78 fs. When we adopted a hydrogen maser as an ultrastable clock (a stability of 6x10 -13 for an integration time τ of 1 s) for PLL operation, we could greatly improve the stability to as high as 8.5×10 -13 for τ=1 s and 5.9×10 -14 for τ=100 s. When we adopted the hydrogen maser clock the stability improved fourteen-fold compared with a conventional synthesizer [4].…”

Polarization Switching in an Active Harmonic Mode Locked Fiber Laser

“…Active mode locking has attracted widespread attention in recent years due to its potential of producing short and high repetition rate pulse sequence, low timing jitter and ease of synchronization to a stable electronic clock signal [1,2]. However, stability of the laser is one of the critical issues, especially when harmonic mode locking is required to obtain repetition rate as high as tens of GHz or higher Super mode noise can cause fluctuation in the amplitude of pulses generated from this kind of laser.…”

“…Several techniques have been proposed to improve the stability of the lasers such as intra cavity filtering regenerative mode locking phase lock-loop feedback control etc. [2,5,6]. However, there are no reports to date addressing the polarization switching phenomena in an active harmonic mode-locked fiber laser.…”

“…Therefore, the polarization of the pulse is switched from x axis to y axis ISBN 978-0-9775657-3-3 when the modulation frequency is tuned from f, to f, The switching of the polarization of the mode-locked pulse train can be attributed to the birefringence property of the laser cavity Since the lightwaves traveling in the X axis sees an effective refractive index n different from ny when traveling in the Y axis the traveling round trip time of the ring is thus different from Xto Y-axis. The laser can thus resonate at two different fundamental frequencies, f for the X axis and Ry for the Y axis instead of a single fundamental frequency as reported in [2][3][4][5]. When the modulation frequency is equal to an integer number multiple of f, the laser is excited and mode locked in the X axis, resulting in the output pulse has X polarized state.…”

Actively mode-locked fiber lasers for high speed telecommunication systems

“…Several techniques have been proposed to stabilize the laser against temperature. A common technique is to adjust the cavity length to compensate for the variation such as in [32,33]. The authors used a piezoelectric drum driven by an error signal to adjust the fiber length.…”