EXTERNAL CAVITY TUNABLE LD LIGHT SOURCE ECL-210
3-1
Features
3
3-1 Tuning Wavelength
The oscillation wavelength can be widely tuned by controlling the loss against the components
in selecting wavelength inside of external cavity module. The way of ECL selecting wave-
length is to make the two independent OBPF and FLF work together. The excellent selectivity
of FLF enables the wavelength of LASER to be locked automatically. This high-precise FLF
control achieves superior wavelength accuracy, stability, and repeatability. OBPF and FLF
are controlled by the control circuit in ECL, and those can be easily operated by setting target
wavelength from external through MLS. For a small amount of wavelength rectification after
setting wavelength, it is possible to set fine tuning independently.
3-2 Coherence Control
The oscillated spectrum linewidth of the ECL-210 is fairly narrow in comparison with normal
semiconductor lasers. Spectrum linewidth is one of the factors that determines light coherence,
and the narrower the spectrum linewidth, the more improved the coherence. Considering the
length of fiber used or the complexity of some test set-ups, there is the possibility that within
the length of fiber in the test set-up there is a reflection point in the optical fiber transmission
system, optical output power changes within the fiber due to interference. To combat this, the
ECL-210 is equipped with a Coherence Control.
Coherence control is radio frequency modulation against the external cavity module, and the
spectrum line width of the narrow sense isn't expanded. However, it effects very much for the
oppression of Brillouin scattering occurred with high optical power and optical power vacilla-
tion by interference in fiber. ECL is equipped with coherence control function for structuring a
stable system on a few residual reflection points and high optical power. The coherent control
enables to control ON/OFF and adjust the level.
0.3dB (p-p)
326.0
306.0
286.0
326.0
306.0
286.0
100sec.
600sec.
without
Coherence
Control
85kHz
FREQUENCY [Hz]
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