JP2789831B2 - Micro-optics optical component with mode field conversion function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a passive component for an optical fiber amplifier, and more particularly to a passive component directly connected to an amplification medium.

[0002]

2. Description of the Related Art A conventional passive component for an optical fiber amplifier is shown in FIG. As is apparent from this figure, the optical fiber amplifier passive component has a mode field diameter of 8 to 10 μm which is generally used as an optical communication transmission line at the signal light input / output port 1 for matching with the transmission line. An optical fiber 2 is used. Here, the mode field diameter is used as a structural parameter of a single mode optical fiber, and the light intensity distribution in the radial direction of the optical fiber is 1 / e (e is the base of natural logarithm; .718
28). On the other hand, general optical fibers 6 and 7 are also used for the pump light input port 3 and the pump light output port 5 directly connected to the amplification medium 4 in accordance with the optical fiber 2. And an amplification medium 4 having a mode field diameter of about 5 μm;
The emission port 5 connected to the amplification medium 4 is connected by a splice (permanent connection) or the like.

[0003]

However, generally, in an optical fiber amplifier, it is necessary to introduce pumping light having a wavelength different from that of signal light into the amplification medium 4 to excite the amplification medium 4. In practice, it is desirable that the excitation light power be small. Therefore, in order to increase the energy density in the amplification medium 4, the mode field diameter of the amplification medium 4 is often reduced to about 5 μm.

To configure an optical fiber amplifier, it is necessary to connect the amplifying medium 4 and the output port 5 of the passive component by a splice or the like as described above. 1 to 2d
B loss occurs. As a result, there has been a problem that characteristics such as gain (amplitude ratio of an output signal to a sine wave input signal having a constant amplitude), saturation output, and noise figure of the optical fiber amplifier are deteriorated.

An object of the present invention is to provide a passive component for an optical fiber amplifier which can improve characteristics such as gain, saturation output, and noise figure.

[0006]

According to the first aspect of the present invention,
Light amplifying signal light to the optical fiber and the amplifying medium directly file
In a micro-optics optical component having a mode field conversion function for an amplifier, an output port directly connected to an amplification medium of an optical fiber amplifier has a light having the same mode field diameter as that of the amplification medium. Use a fiber with a mode field diameter different from the mode field diameter used for the excitation light input port in the fiber, and independently adjust the image magnification for the input port and output port regardless of the difference in these mode field diameters This is characterized in that a dedicated lens is arranged to convert a different mode field diameter between the entrance port side and the exit port side arranged via the optical element.

[0007]

[0008]

[0009]

According to the present invention, dedicated lenses for independently adjusting the image magnification are arranged on the entrance port side and the exit port side, and
To carry out the conversion of the mode field diameter differs in output port side and the entrance port side arranged through Manabu element
Was. This makes it possible to reduce the loss at the connection point. As a result, characteristics such as gain, saturation output, and noise figure of the optical fiber amplifier can be improved.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

FIG. 1 shows a passive component for an optical fiber amplifier .
This shows an outline in which a micro-optics optical component as a component having a mode field conversion function is applied to a polarization independent optical isolator. In this embodiment, the optical element 10 is a polarization-independent isolator element, and an incident-side lens 11 and an output-side lens 12 are arranged on both left and right sides of the optical element 10. An excitation light input port 13 is disposed on the left side of the incident side lens 11, and an excitation light output port 14 is disposed on the right side of the output side lens 12. This emission port 1
4 is directly connected to the amplification medium 15.

The amplification medium 15 includes erbium (E
r ³⁺ ) doped fiber having a mode field diameter of 5 μm. Also, the excitation light input port 1
A dispersion shift fiber 16 having a mode field diameter of 8 μm is used for 3, and an optical fiber 17 having a mode field diameter of 5 μm which is the same as that of the amplification medium 15 is used for an emission port 14 of the excitation light. The entrance port 13 and exit port 14 having different mode field diameters are optimally (low loss) coupled by adjusting the image magnification of the entrance side lens 11 and exit side lens 12.

At a connection point 18 between the amplifying medium 15 and the output port 14 directly connected to the amplifying medium 15, optical fibers having a mode field diameter of 5 μm are connected to each other by a splice, and the connection loss is 0.1. ~ 0.2d
B and low loss.

FIG. 2 shows an embodiment in which the optical fiber amplifier of the present invention is applied to a wavelength coupler having a function of combining or dispersing excitation light and signal light, and the optical element 19 is a wavelength combining or dispersion film. An entrance lens 20 and an exit lens 21 are arranged on both left and right sides of the optical element 19. The left side of the entrance lens 20 and the exit lens 2
An excitation light input port 22 and an excitation light output port 23 are respectively disposed on the right side of 1. This emission port 23 is directly connected to an amplification medium 25 at a connection point 24. In addition, an input / output port 27 for signal light is disposed below the optical element 19 via an incident-side lens 26.

The amplification medium 25 is an erbium-doped fiber, has a mode field diameter of 5 μm, and has an output port 23 directly connected to the amplification medium 25.
The optical fiber 28 used in this embodiment also uses an optical fiber having the same mode field diameter of 5 μm as the amplification medium 25. Dispersion shift fibers 29 and 30 having a mode field diameter of 8 μm are used for the excitation light input port 22 and the signal light input / output port 27.

As the pump light input port 22 and the signal light input / output port 27, a general single mode fiber, polarization maintaining fiber, or the like may be used in addition to the above-described dispersion shift fibers 29 and 30. The optical elements 10 and 19 differ depending on the type of passive component, and may be an element such as an optical filter in addition to the above-described polarization-independent isolator element, wavelength combining or separation film.

As the amplification medium, in addition to the above-mentioned erbium-doped fiber, rare-earth-doped fiber such as Nd-doped fiber and Tm-doped fiber, silica fiber used for fiber Raman amplification, and silica fiber used for fiber burrian amplification are also available. Conceivable. In this case, an optical fiber having the same mode field diameter as the fiber used for the amplification medium is used for the exit port of the excitation light directly connected to the amplification medium.

[0018]

As described above, according to the micro-optics optical component having the mode field conversion function of the present invention, the mode filter is provided on the input port side and the output port side .
Specially adjusts the image magnification independently of the difference in the field diameter.
In this case, the adjustment of the image magnification can be independently performed by arranging a lens for the input and output, so that a different mode field diameter can be converted between the entrance port side and the exit port side. This makes it possible to reduce the loss at the connection point. As a result, characteristics such as gain, saturation output, and noise figure of the optical fiber amplifier can be significantly improved. Moreover, there is an excellent effect that the present invention can be applied to various optical elements.

──────────────────────────────────────────────────の Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01S 3/07 G02B 6/00 G02B 6/24 H01S 3/094 H01S 3/10 G02F 1/35 501 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A mode-field converter for an optical fiber amplifier that directly amplifies signal light using an optical fiber as an amplification medium.
In micro optics type optical components with functions ,
At the output port directly connected to the amplification medium of the optical fiber amplifier , an optical fiber having the same mode field diameter as this amplification medium and having a mode field diameter different from the mode field diameter used at the excitation light input port. , And independently image the entrance and exit ports regardless of the difference in these mode field diameters.
A mode field conversion function characterized in that a dedicated lens for adjusting the magnification is arranged to convert a different mode field diameter between the entrance port side and the exit port side arranged via the optical element. Micro optics type optical components.