3-4
ECL-210 OPERATION MANUAL
3-4-3. ACC Mode
In ACC mode, ECL controls with set current in advance. It is possible to stabilize optical
power by adding the feedback signals from external optical power criteria into low frequency
modulation terminal. Note that optical power may fluctuate extremely depending on external
modulation signal input.
I=Const.
ACC mode
Optical output power
Wavelength
3-5 Built-in Attenuator
3-5-1. Introduction
By adopting an external cavity structure the product has maintained various semiconductor
laser features. In particular this structure makes it possible to tune the wavelength of the laser
light. However, the optical output power is controlled by tuning the LD injection current.
This causes a change in the optical path length in the LD that can consequently cause an opti-
cal wavelength shift or cause difficulty in maintaining adequate SSR (side-mode suppression
ratio). To counter these problems, a tunable attenuator (ATT) is fitted on the output side of the
external cavity. The data below shows a comparison of the spectrum of the output signal with
the output power set to -15dB with and without the attenuator.
Without ATT
With ATT
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