JPH11330593A - Broadband spontaneous emission type optical source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a practical optical source allowing the band to broaden up to about 1530-1610 nm. SOLUTION: The optical source comprises an optical amplifier fiber 1 of Er doped fiber, etc., and exciting light input means disposed at the start and tail ends of the optical amplifier fiber 1 for inputting an exciting light. The optical amplifier fiber 1 has a length or absorption characteristic that mainly short wavelength components are absorbed and long wavelength components remain until a spontaneous emission light generated at the start end runs to the tail end and outputs from the tail end both the spontaneous emission light generated by the exciting light at the start end to propagate on the optical amplifier fiber 1 and that generated by the exciting light at the tail end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadband spontaneous emission light source using a spontaneous emission light generated from an excited optical amplification fiber as a light source. (WDM) suitable for use as a light source in an optical communication system.

[0002]

2. Description of the Related Art In recent years, with the expansion of communication capacity, wavelength division multiplexing (WDM) optical fiber communication systems for multiplexing and transmitting and receiving optical signals having different wavelengths using a wide wavelength band have been actively studied. Against this background, erbium-doped optical fiber amplifiers (ED
Broadband spontaneous emission light source using ASE (Amplified Spontaneous Emission) of FA: Erbium Doped fiber Amplifler (ASE) is used as a light source for incoherent WDM and as a light source for testing optical components for WDM system. ing. As a light source using spontaneous emission light, for example, JP-A-8-46297 and JP-A-9-
There is one described in Japanese Patent No. 232661. Japanese Patent Application Laid-Open No. 9-232661 discloses a 1.5 μm band WDM.
For this purpose, a broadband light source with a spectral width of 38 nm centered at 1.55 μm has been reported.

[0003]

[Problems to be Solved by the Invention] However, Optical Fi
ber Communication Conference 98 Postdeadline Paper
An optical amplifier and an optical communication system with a wavelength band of about 1530 to 1610 nm have been reported (AKSrivastava et al.
al. "1Tb / s Transmission of 100 WDM 10Gb / s Channels
Over 400km of True Wave Fiber. ", PD10," S. Aisawa,
et al. "Ultra-wide band, long distance WDM transm
ission demonstration: 1Tb / s (50x20Gb / s) .600km trans
mission using 1550 and 1580nm wavelength bands. ",
PD11), light sources have been required to have a broadband from about 1530 to 1565 nm to about 1530 to 1610 nm. At present, such broadband light sources are being studied for practical use, but none of them has a simple structure and is suitable for practical use.

[0004]

According to a first aspect of the present invention, there is provided a broadband spontaneous emission light source, comprising: an optical amplification fiber such as an erbium-doped fiber; and an excitation light input to a start end and an end of the optical amplification fiber. Light input means, and the optical amplification fiber has a length or absorption characteristic in which short wavelength components are mainly absorbed and long wavelength components remain until spontaneous emission light generated on the start side reaches the end side, The spontaneous emission light generated by the pump light from the start end and propagated through the optical amplification fiber and the spontaneous emission light generated by the excitation light from the end side are both output from the end side of the optical amplification fiber. It is characterized by having done.

In the broadband spontaneous emission light source according to the second aspect of the present invention, of the spontaneous emission light output from the terminal end of the optical amplification fiber, the light emitted mainly by the excitation light at the start end is mainly 1570.
It is a long wavelength band light of nm or more, and the light by the excitation light on the terminal side is mainly a short wavelength band light of 1530 to 1570 nm.

According to a third aspect of the present invention, there is provided the broadband spontaneous emission light source, wherein the light intensity ratio between the pump light input to the starting end of the optical amplification fiber and the pump light input to the terminal end is 1: 3 or more. It is assumed that.

The broadband spontaneous emission light source according to claim 4 of the present invention reduces the absorption loss at 1.53 μm of the optical amplification fiber.
It is characterized by being set to 800 dB or more.

In the broadband spontaneous emission light source according to a fifth aspect of the present invention, a compensation filter is provided at an end of the optical amplification fiber to eliminate wavelength dependence of the spontaneous emission output from the end. It is characterized by the following.

[0009]

(Embodiment 1) FIG. 1 is a schematic view of an embodiment of a broadband spontaneous emission light source according to the present invention. The optical amplification fiber 1, first and second excitation light sources 2a and 2b, and 1,
It comprises a second wavelength multi-wave device 3a, 3b, an optical output port 4, and a non-reflection end 5. The first and second pumping light sources 2a and 2b and the first and second multi-wavelength wavelength-multiplexing devices 3a and 3b constitute pumping light input means for inputting pumping light to the start and end of the optical amplification fiber 1. .

The optical amplification fiber 1 is an erbium-doped optical fiber having an absorption intensity of 936 dB at a fiber length of 360 m and a wavelength of 1.5 μm (EDFA absorption coefficient (@ 1.53 μm) 2.6 dB /
m). This optical amplification fiber 1 has the characteristics shown in FIG. 4 in relation to the average inversion distribution η and the spontaneous emission light spectrum, and 1530 to 1570 nm in a region where the average inversion distribution η is 0.5 or more.
, The spontaneous emission light is generated at a wavelength of 1570 nm or more in a region where the average population inversion η is 0.5 or less. In addition, since spontaneous emission light in a short wavelength band is easily absorbed by erbium ions in the optical amplification fiber 1,
In the optical amplifying fiber 1 of FIG. 1, even if spontaneous emission light of a short wavelength is generated at the start end, it hardly reaches the end side, and only the spontaneous emission light of the long wavelength band reaches.

The first and second excitation light sources 2a and 2b have a wavelength of 1480 nm.
Bandwidth semiconductor laser diodes are used. In the 1.5 μm band optical communication using this light source, a laser having an oscillation wavelength in the 980 nm band is used, but a laser having this wavelength may be used.

The first wavelength multiplexing device 3a enables the excitation light generated by the first pumping light source 2a to be incident on the starting end of the optical amplification fiber 1, and the second wavelength multiplexing device 3a. 3
“b” allows the excitation light generated by the second excitation light source 3b to be incident on the end of the optical amplification fiber 1. As these wavelength-multiplexed wave devices 3a and 3b, desired ones can be used from among a filter type, a fusion type and the like, but a filter type having a wide band and little wavelength dependence of loss characteristics is desirable.

The non-reflection end 5 is for preventing light propagating to the side opposite to the output port 4 from leaking outside, and can be replaced by an optical isolator.

In the above configuration, the first excitation light source 2a
Has a light intensity of 170 mW, and the second excitation light source 2b has a light intensity of 34 mW.
mW (the light intensity ratio of both light sources is 1: 5), and when both light sources 2a and 2b are operated to input pump light to both ends of the optical amplification fiber 1, an average is obtained in the section 1a shown in FIG. When the population inversion η becomes 0.5 or more, spontaneous emission light mainly having a short wavelength of 1520 to 1570 nm is generated.
Is 0.5 or less, spontaneous emission light having a long wavelength of 1570 nm or more is generated. Spontaneous emission light is obtained, and this light is output from the output port 4.

When only the first excitation light source 2a is operated in the apparatus shown in FIG.
When only the second excitation light source 2b is operated, only the short-wavelength spontaneous emission light as shown in FIG. 3 (b) is output. In FIG. 3 (c), the composite does not have a curve Y, but has a lower flatness than the actually obtained curve X (the band is not broadened). This is because when the two pump light sources 2a and 2b are operated, spontaneous emission light generated by the pump light from the terminal side of the optical amplification fiber 1 and having a short wavelength enters the section 1a of FIG. This is because the optical amplification fiber 1 in the section 1a is excited by the synergistic effect of 2b, and spontaneous emission light in a long wavelength band is generated more effectively.

(Embodiment 2) FIG. 2 shows another embodiment of the broadband spontaneous emission light source according to the present invention, which has the same configuration as that of FIG. 1 and has a compensation filter 6 inserted before the output port 4 thereof. Things. The compensating filter (spectral equivalent filter) 6 uses two Mach-Zehnder filters, each having an FSR (free spectral range) of 100 nm and a center wavelength of 1560 nm and 1593 nm, respectively.
By inserting the compensation filter 6, as shown in FIG. 5, flat spontaneous emission light in a wide band of 82 nm as a 3 dB band was obtained.

The broadband spontaneous emission light source of the present invention may have a configuration in which a single excitation light source is used, and the light from this light source is distributed and input to the start and end of the optical amplification fiber 1.
In this case, a difference is made between the light intensities of the excitation lights input to the start end and the end, and for example, the light intensity is set to 170 mW as in the first embodiment.
34 mW. However, since there is no semiconductor LD with an output of 170 + 34 mW at present, a single pumping light source is configured to combine the outputs of two semiconductor LDs with a coupler.

In the present invention, the pumping light input to the start and end of the optical amplification fiber 1 can have different wavelengths.

[0019]

According to the broadband spontaneous emission light source of the present invention, the following effects can be obtained. . Although it has a simple configuration, it can generate uniform spontaneous emission light in a wide band, and has a wide band WDM.
Can be used for . Because of the simple structure, the reliability of the device is high, the cost can be kept low, and miniaturization and maintenance can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a first embodiment of a broadband spontaneous emission light source according to the present invention.

FIG. 2 is a schematic diagram showing a second embodiment of the broadband spontaneous emission light source of the present invention.

3A and 3B are explanatory diagrams showing a spectrum of light output from an output port, where FIG. 3A shows an output when a starting end pumping light source is operated, and FIG. (C) shows the output when both pumping light sources are operated.

FIG. 4 is an explanatory diagram showing the relationship between the average population inversion distribution of the optical amplification fiber and the spontaneous emission light spectrum.

FIG. 5 is an explanatory diagram showing a spectrum of spontaneous emission light obtained by the broadband spontaneous emission light source of FIG. 2;

[Explanation of symbols]

 1 Optical amplification fiber

Claims (5)

[Claims] An optical amplification fiber comprising: an optical amplification fiber having an action of amplifying light by stimulated emission of an erbium-doped fiber; and excitation light input means for inputting excitation light to a start end and an end of the optical amplification fiber. The length of the spontaneous emission light generated at the start end is of a length or absorption characteristic in which the short wavelength component is mainly absorbed and the long wavelength component remains until it reaches the end side, and is generated by the excitation light from the start end. The spontaneous emission light propagated through the optical amplification fiber and the spontaneous emission light generated by the excitation light from the terminal side are both output from the terminal side of the optical amplification fiber. light source. 2. Of the spontaneous emission light output from the terminal side of the optical amplifying fiber, one mainly due to the pumping light on the start side is 1570.
2. The broadband spontaneous emission light source according to claim 1, wherein the light is a long wavelength band light of at least nm and is mainly a short wavelength band light of 1530 to 1570 nm due to the excitation light on the terminal side. 3. The wide-band natural light according to claim 1, wherein a light intensity ratio between the pump light input to the start end of the optical amplification fiber and the pump light input to the terminal end is 1: 3 or more. Emission light source. 4. The absorption loss of the optical amplification fiber at 1.53 μm.
4. The broadband spontaneous emission light source according to claim 1, wherein the power is 800 dB or more. 5. The optical amplifying fiber according to claim 1, further comprising a compensating filter provided at an end of said optical amplifying fiber for eliminating wavelength dependence of spontaneous emission light output from said end.
The broadband spontaneous emission light source according to any one of the above.