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High-output excitation laser diode module

In the current optical communication system, an optical amplifier (EDFA) which uses an erbium (Er)(Note 1) doped fiber as a medium, is used to amplify the attenuated optical signal. EDFA requires an Er ion excitation light source, and excitation light sources of 980 nm for low noise usage and of 1480 nm for high-output usage are applied.

In the case of the next generation optical communication system using the digital coherent transmission method, the Raman amplifier utilizing a transmission line as amplifying medium is an important technology. The Raman amplifier, according to the principles of Brillouin scattering (Note 2), utilizes a transmission line as amplifying medium and excellent in noise characteristic. This amplifier has a feature that any wavelength can be amplified by using almost 100 nm shorter wavelength, from 1400 nm to 1500 nm band, than the signal wavelength as excitation light source (14xx nm LDM). By achieving stabilization of Fiber Bragg Grating (FBG) (Note 3), severe requirement for wavelength stability is satisfied.

By making full use of semiconductor crystal growth technology and high precision module assembly technology which have been cultivated for many years, Furukawa electric offers excitation light sources that exceed 500 mW. Especially, the latest model of 14xx-nm LDM achieves 40% reduction of electric power consumption in comparison with the initial stage products.


Feature

  • The excitation light source featured by high-output, high-reliability and low electric power consumption operation.
  • Both 980 nm and 1480 nm as excitation light sources for EDFA are in the line-up.
  • 14xx nm exciting light source, in wide wavelength range (from 1400 nm to 1500 nm), for the Raman amplifier is in the line-up.
  • High-output is achieved. 980 nm light source: max. 550mW, 1480nm light source: Max. 500mW
  • Excellent operational stability based on the double FBG structure.

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1480/14xxLDM
1480/14xx nm Appearance of the laser module.

Relation between laser light output and power consumption
Relation between laser light output and power consumption

(Note 1) Erbium (Chemical symbol Er, Atomic number 68) is one ob the rare–earth elements. The crystal structure is a Hexagonal close-packed structure. By irradiating light of 1.48 nm, its energy level rises temporarily and release light of 1.55 nm when energy returns to the original state. Utilizing this phenomenon, light used to optical transmission can be amplified.

(Note 2) Stimulated Brilliant Scattering (SBS): The non-linear optical phenomenon generated in optical fiber. When light proceeds in an optical fiber, light is scattered in the opposite direction to the proceeding direction. And the proceeding light hit the optical fiber and a phonon is induced. The scattered light is amplified on proceeding by the interaction of the insertion light and the phonon, in the case of the insertion light which exceeds a certain level of strength, most of the insertion light comes back to the insertion end as scattered light. This behavior is called stimulated Brilliant scattering. The name is derived from Leon Brilliant.

(Note 3) Fiber Bragg Grating (FBG): This means a fiber type devices; periodic refractive index change is formed in the core of the optical fiber. Refractive index in the core of the fiber is changed by using Excimer laser and the structure of diffraction grating structure is written in the optical fiber. Only the light of the wavelength, which satisfies the reflection condition decided by the cycle of the diffraction grating, can be reflected. Therefore, this can be a powerful device to correct the wavelength, when a delicate control to fix the wavelength is required, like a tunable laser.

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