S+c+l-band ultra-wideband gain active optical fiber

Abstract

An S+C+L-band ultra-wideband gain active optical fiber. The optical fiber sequentially comprises, from inside to outside, an inner core layer (1), an inner cladding layer (2), a core layer (3), a loose layer (4) and a cladding layer (5), wherein the inner core layer (1) is doped with Tm ions, the inner cladding layer (2) is doped with F elements, the core layer (3) is doped with Er ions, and the loose layer (4) is doped with Bi, Al and P ions. In the structure of the optical fiber, the Tm ions of the inner core layer (1) are completely wrapped by the inner cladding layer (2) doped with F elements, such that the Tm ions are in a low-phonon energy environment provided by the F elements, thereby improving the light-emission efficiency of the Tm ions in an S band. The core layer (3) is coated with the loose layer (4) and the inner cladding layer (2), such that the contact between the Er ions in the core layer (3) and the Tm ions in the inner core layer (1) is blocked, thereby reducing the energy transfer probability, reducing the mutual influence between the Tm ions and the Er ions, and improving the light-emission efficiency of the Er ions and the Tm ions in S, C and L bands.

Description

S+C+L band ultra-wideband gain active fiber Technical Field

[0001] The invention belongs to the field of optical fiber communication and optical fiber technology, and particularly relates to an Er / Tm / Bi / F co-doped optical fiber core structure. Background Art

[0002] In recent years, the increasing volume of data transmitted by optical communication systems, coupled with the continuous advancement of fiber-optic communication technology and the maturation of DWDM technology, has placed increasing demands on optical amplification technologies within the communication window band. The traditional C-band bandwidth is no longer sufficient for communication systems. The demand for higher-capacity optical communication systems has led to the exploration of optical amplification within the S- and L-bands. Therefore, the development of ultra-wideband active amplified optical fibers encompassing the S+C+L bands would significantly expand the capacity of communication systems.

[0003] In 2015, Chinese patent 201510941655.3 proposed using atomic deposition technology (ALD) to alternately deposit Bi and Er ions or Bi, Er, and Al ions to prepare a concentration-controllable co-doped silica fiber, which can achieve ultra-wideband amplification in the C+L band. In 2018, Chinese patent 201711327868.2 proposed a fiber amplifier made of thulium-dysprosium co-doped bismuth laser glass to achieve S-band broadband amplification. In 2020, Chinese patent 202010073619.0 proposed using improved chemical vapor deposition technology (MCVD) combined with other processes to prepare Bi / Er / La / Al co-doped silica fiber, which can achieve ultra-wideband luminescence in the L band or C+L band. In 2020, Chinese patent 202010551558.4 proposed the use of a solution method combined with the MCVD process to prepare broadband gain erbium-doped optical fiber, which has ultra-wideband high gain characteristics in the range of 1510-1580nm. In 2021, Chinese patent 201911335359.3 proposed a method for preparing Er / Yb / P co-doped glass core rods based on nanoporous technology, which achieved the expansion of the luminescence bandwidth of Er ions to the S band, thereby realizing broadband luminescence in the S and C bands. The content of the above patents mostly focuses on broadband amplification in the C+L or S+C bands, and cannot achieve S+C+L super-band broadband amplification. The reason is that the doping of Tm ions in the S band requires a low phonon energy environment to have better luminescence characteristics, and the quartz matrix does not meet the requirements of a low phonon energy environment. Moreover, the co-doping of Tm ions and Er ions will inevitably produce energy transfer from Er ions to Tm ions, reducing the luminescence efficiency of Er ions in the C+L band and causing the C+L band bandwidth to narrow. Summary of the Invention

[0004] The present invention addresses the technical problems of the prior art, addressing the aforementioned shortcomings by providing a low-phonon energy environment for Tm ions and preventing energy transfer between Er and Tm ions. By designing a multi-layered optical fiber structure, the inner cladding containing F elements provides a low-phonon energy environment for Tm ions while also preventing energy transfer from Er to Tm ions. This also improves the luminescence efficiency of both Er and Tm ions, achieving ultra-broadband S+C+L gain.

[0005] The technical solution of the present invention:

[0006] S+C+L band ultra-wideband gain active optical fiber, the optical fiber includes inner core layer, inner cladding, core layer, loose layer and cladding from the inside to the outside. The inner core layer is doped with Tm ions, the inner cladding is doped with F elements, the core layer is doped with Er ions, and the loose layer is doped with Bi, Al and P ions.

[0007] Using optical fiber fabrication techniques, dopant elements are sequentially deposited within a quartz substrate to form an inner core layer, inner cladding layer, core layer, loose layer, and cladding layer structure. Tm ions emit in the S band, while Er ions emit in the C+L band. Co-doping these two rare earth elements superimposes emission peaks, ensuring broadband emission in the S+C+L bands. Within the fiber structure, the Tm ions in the inner core layer are completely encapsulated by the inner cladding formed by the F element, exposing them to a low-phonon energy environment provided by the F element and enhancing their S-band luminescence efficiency. The core layer, sandwiched between the loose layer and inner cladding, blocks contact between Er ions in the core layer and Tm ions in the inner core layer, reducing the probability of energy transfer and the mutual influence between Tm and Er ions, thereby enhancing the luminescence efficiency of Er and Tm ions in the S, C, and L bands.

[0008] The Er ion doping concentration range is controlled within 0.01~4mol%; the Tm ion doping concentration range is controlled within 0.01~2mol%; the Bi ion doping concentration range is controlled within 0.01~1.5mol%; the F ion doping concentration range is controlled within 0.01~1mol%; the Al ion doping concentration range is controlled within 0.01~10mol%; and the P ion doping concentration range is controlled within 0.01~10mol%.

[0009] The optical fiber structure can be summarized as a core and a cladding. The core includes an inner core layer, an inner cladding layer, a core layer, and a loose layer. The core diameter is 4 to 25 μm, the cladding diameter is 70 to 250 μm, and the refractive index difference between the core and cladding is between 0.002 and 0.05.

[0010] The optical fiber's absorption wavelength range is 450 to 1625 nm; its emission wavelength range is 1260 to 1650 nm; its gain greater than 20 dB is from 1460 to 1625 nm, and its noise figure is below 5 dB. This achieves ultra-wideband gain in the S+C+L bands.

[0011] The beneficial effects of the present invention are:

[0012] 1. The Er / Tm / Bi / F co-doping elements and unique fiber structure of the fabricated S+C+L band ultra-wideband gain-active fiber effectively enhance the luminescence efficiency of rare earth ions in the corresponding wavelength bands. By improving the fiber structure, the F element deposited in the inner cladding coats the Tm ions in the inner core layer, placing the Tm ions in an environment with extremely low phonon energy, thereby ensuring efficient S-band luminescence from the Tm ions. Furthermore, the energy transfer probability between Er and Tm ions is reduced, minimizing the impact of Tm ions on the C+L band luminescence bandwidth of Er ions. The superposition of the Tm and Er ion luminescence bands enables the fiber as a whole to achieve ultra-wideband amplification in the S+C+L band.

[0013] 2. The prepared S+C+L band ultra-wideband gain active optical fiber has low background loss, high absorption intensity, and the characteristics of high gain and low noise in the S+C+L band.

[0014] 3. The optical fiber preparation process is simple and inexpensive, and can be widely used in optical fiber communication devices such as optical amplifiers, broadband light sources, fiber lasers and tunable lasers. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram of the structure of the optical fiber of the present invention, wherein (1) is the inner core layer, (2) is the inner cladding layer, (3) is the core layer, (4) is the loose layer, and (5) is the cladding layer.

[0016] FIG2 is a gain diagram of the optical fiber prepared by the present invention. DETAILED DESCRIPTION

[0017] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0018] Example 1:

[0019] Referring to Figure 1, the S+C+L band ultra-wideband gain active fiber uses high-temperature chemical vapor deposition to introduce Bi, Al, and P ions onto SiO2 deposited on the inner wall of a quartz tube to form a loose layer. A large amount of Er ions is then introduced into the quartz tube to deposit on the loose layer as the core layer. F ions are then introduced to cover the core layer as the inner cladding. Tm ions are then introduced to form the inner core layer. Finally, the rod is shrunk at high temperature and drawn into the fiber using a drawing tower. The prepared fiber has a core diameter of 9.1 μm and a cladding diameter of 126.1 μm. The Er ion doping concentration is 0.4 mol%, the Tm ion doping concentration is 0.2 mol%, the Bi doping concentration is 0.1 mol%, the F ion doping concentration is 0.05 mol%, the Al ion doping concentration is 0.5 mol%, and the P ion doping concentration is 1 mol%.

[0020] See FIG2 , which is a gain diagram of Example 1 of an S+C+L band ultra-wideband gain active optical fiber. This example can achieve S+C+L band broadband amplification.

[0021] Example 2:

[0022] Referring to Figure 1, the S+C+L band ultra-wideband gain active fiber uses high-temperature chemical vapor deposition to introduce Bi and Al ions onto SiO2 deposited on the inner wall of a quartz tube to form a loose layer. A large amount of Er ions is then introduced into the quartz tube, depositing them on the loose layer as the core layer. F ions are then introduced to cover the core layer, forming the inner cladding. Tm ions are then introduced to form the inner core layer. Finally, the rod is shrunk at high temperature and drawn into the fiber using a drawing tower. The resulting fiber has a core diameter of 8.9 μm and a cladding diameter of 125.4 μm. The Er ion doping concentration is 0.4 mol%, the Tm ion doping concentration is 0.2 mol%, the Bi doping concentration is 0.1 mol%, the F ion doping concentration is 0.05 mol%, and the Al ion doping concentration is 0.5 mol%.

[0023] See FIG2 , which is a gain diagram of Example 2 of an S+C+L band ultra-wideband gain active optical fiber. This example can achieve S+C+L band broadband amplification.

Claims

1. An S+C+L band ultra-wideband gain active optical fiber, characterized in that: The optical fiber includes an inner core layer, an inner cladding layer, a core layer, a loose layer and a cladding layer from the inside to the outside. The inner core layer is doped with Tm ions, the inner cladding layer is doped with F elements, and the core layer is doped with Er ions.

2. The S+C+L band ultra-wideband gain active optical fiber according to claim 1, characterized in that: The loose layer is doped with Bi, Al and P ions.

3. The S+C+L band ultra-wideband gain active optical fiber according to claim 2, characterized in that: The Er ion doping concentration range is controlled within 0.01~4mol%; the Tm ion doping concentration range is controlled within 0.01~2mol%; the Bi ion doping concentration range is controlled within 0.01~1.5mol%; the F ion doping concentration range is controlled within 0.01~1mol%; the Al ion doping concentration range is controlled within 0.01~10mol%; and the P ion doping concentration range is controlled within 0.01~10mol%.

4. The S+C+L band ultra-wideband gain active optical fiber according to claim 2, characterized in that: The inner core layer, inner cladding layer, core layer and loose layer constitute the fiber core, the core diameter is 4 to 25 μm, and the cladding diameter is 70 to 250 μm.

5. The S+C+L band ultra-wideband gain active optical fiber according to claim 4, characterized in that: The refractive index difference between the core and the cladding is between 0.002 and 0.

05.

6. The S+C+L band ultra-wideband gain active optical fiber according to any one of claims 3 to 5, characterized in that: The absorption wavelength range of the optical fiber is 450-1625nm; the emission wavelength range is 1260-1650nm; the wavelength range with gain greater than 20dB is 1460-1625nm, and the noise coefficient is less than 5dB.

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