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

Abstract

This invention discloses an S+C+L band ultra-wideband gain active optical fiber. The fiber comprises, from the inside out, an inner core layer, an inner cladding layer, a core layer, a loose layer, and a cladding layer. The inner core layer is doped with Tm ions, the inner cladding layer is doped with fluorine (F), the core layer is doped with Er ions, and the loose layer is doped with Bi, Al, and P ions. In the fiber structure, the Tm ions in the inner core layer are completely encapsulated by the F-formed inner cladding, placing the Tm ions in a low phonon energy environment provided by F, thus improving its S-band luminous efficiency. The core layer is encapsulated by the loose layer and the inner cladding, blocking the contact between Er ions in the core layer and Tm ions in the inner core layer, reducing the energy transfer probability, minimizing the interaction between Tm and Er ions, and improving the luminous efficiency of Er and Tm ions in the S, C, and L bands.

Description

Technical Field

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

[0002] In recent years, with the increasing data volume transmitted by optical communication systems and the continuous development of fiber optic communication technology, as well as the increasing maturity of DWDM technology, many requirements have been placed on optical amplification technology within the communication window band. The traditional C-band bandwidth can no longer meet the needs of communication systems, and the demand for higher-capacity optical communication systems has spurred exploration of optical amplification in the S-band and L-band. Therefore, if ultra-wideband active amplification optical fibers in the S+C+L bands can be fabricated, the capacity of communication systems will be effectively expanded.

[0003] In 2015, Chinese patent 201510941655.3 proposed using atomic deposition (ALD) technology to alternately deposit Bi and Er ions or Bi, Er, and Al ions to prepare a co-doped silica fiber with controllable concentration, which can achieve ultra-wideband amplification in the C+L band. In 2018, Chinese patent 201711327868.2 proposed a fiber amplifier using thulium-dysprosium co-doped bismuthate laser glass to achieve S-band broadband amplification. In 2020, Chinese patent 202010073619.0 proposed using modified chemical vapor deposition (MCVD) combined with other processes to prepare Bi / Er / La / Al co-doped silica fiber, which can achieve ultra-wideband light emission in the L-band or C+L band. In 2020, Chinese patent 202010551558.4 proposed a method for fabricating broadband-gain erbium-doped optical fibers using a solution method combined with MCVD technology. This fiber exhibits ultra-wideband, high-gain characteristics in the 1510–1580 nm range. In 2021, Chinese patent 201911335359.3 proposed a method for preparing Er / Yb / P co-doped glass core rods based on nanoporous technology, which extended the luminescence bandwidth of Er ions to the S-band, thereby achieving broadband luminescence in both the S and C bands. Most of these patents focus on broadband amplification in the C+L or S+C bands, failing to achieve ultra-wideband amplification in the S+C+L band. This is because doping with Tm ions in the S-band requires a low-phonon-energy environment to achieve good luminescence characteristics, and the quartz matrix does not meet this requirement. Moreover, co-doping of Tm ions and Er ions inevitably leads to energy transfer from Er ions to Tm ions, which reduces the luminescence efficiency of Er ions in the C+L band and results in a narrower bandwidth in the C+L band. Summary of the Invention

[0004] The technical problem to be solved by this invention is as follows: Addressing the deficiencies of the prior art, this invention solves the problems of providing a low phonon energy environment for Tm ions and preventing energy transfer between Er and Tm ions. By designing a multi-layered fiber structure, an inner cladding containing F elements provides a low phonon energy environment for Tm ions while simultaneously preventing energy transfer from Er to Tm ions; at the same time, it improves the luminescence efficiency of both Er and Tm ions, achieving an ultra-wideband gain of S+C+L.

[0005] The technical solution of this invention:

[0006] The S+C+L band ultra-wideband gain active fiber consists of an inner core, an inner cladding, a core, a loose layer, and a cladding, arranged from the inside out. The inner core is doped with Tm ions, the inner cladding is doped with F, the core is doped with Er ions, and the loose layer is doped with Bi, Al, and P ions.

[0007] Using optical fiber fabrication techniques, doping elements are sequentially deposited in a quartz substrate to form an inner core layer, inner cladding layer, core layer, loose layer, and cladding structure. Tm ions emit light in the S-band, while Er ions emit light in the C+L band. Co-doping with these two rare earth elements causes the emission peaks to overlap, ensuring broadband emission in the S+C+L bands of the optical fiber. In the fiber structure, the Tm ions in the inner core layer are completely encapsulated by the inner cladding formed by fluorine (F) elements, placing the Tm ions in a low phonon energy environment provided by F, thus improving their S-band luminescence efficiency. The core layer, sandwiched between the loose layer and the inner cladding layer, blocks the contact between Er ions in the core layer and Tm ions in the inner core layer, reducing the energy transfer probability and minimizing the interaction between Tm and Er ions, thereby improving the luminescence efficiency of Er and Tm ions in the S, C, and L bands.

[0008] The concentration of Er ions was controlled within the range of 0.01–4 mol%; the concentration of Tm ions was controlled within the range of 0.01–2 mol%; the concentration of Bi ions was controlled within the range of 0.01–1.5 mol%; the concentration of F ions was controlled within the range of 0.01–1 mol%; the concentration of Al ions was controlled within the range of 0.01–10 mol%; and the concentration of P ions was controlled within the range of 0.01–10 mol%.

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

[0010] The optical fiber has an absorption wavelength range of 450–1625 nm, an emission wavelength range of 1260–1650 nm, and a gain greater than 20 dB in the wavelength range of 1460–1625 nm, with noise figures all below 5 dB. Ultra-wideband gain in the S+C+L bands has been achieved.

[0011] The beneficial effects of this invention are as follows:

[0012] 1. The Er / Tm / Bi / F co-doped elements and special fiber structure of the fabricated S+C+L band ultra-wideband gain active fiber effectively improve the luminescence efficiency of rare earth ions in the corresponding 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 the efficient luminescence of Tm ions in the S band. Moreover, it reduces the energy transfer probability between Er and Tm ions, 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 fiber has low background loss and high absorption intensity, and exhibits high gain and low noise characteristics in the S+C+L band.

[0014] 3. Optical fiber manufacturing process is simple and inexpensive, and it can be widely used in optical fiber communication devices such as optical amplifiers, broadband light sources, fiber lasers and tunable lasers. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the optical fiber of the present invention. In it, (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] Figure 2 This is a gain diagram of the optical fiber prepared according to the present invention. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0018] Example 1:

[0019] See Figure 1The S+C+L band ultra-wideband gain active fiber was fabricated by introducing Bi, Al, and P ions into a SiO2 layer deposited on the inner wall of a quartz tube using high-temperature chemical vapor deposition (HTCVD) to form a loose layer. Then, a large number of Er ions were introduced into the quartz tube and deposited onto the loose layer to form the core layer. F ions were then introduced to cover the core layer as the inner cladding, followed by the introduction of Tm ions to form the inner core layer. Finally, the fiber was drawn using a high-temperature drawing tower. The fabricated fiber had a core diameter of 9.1 μm and a cladding diameter of 126.1 μm. The Er ion doping concentration was 0.4 mol%, the Tm ion doping concentration was 0.2 mol%, the Bi doping concentration was 0.1 mol%, the F ion doping concentration was 0.05 mol%, the Al ion doping concentration was 0.5 mol%, and the P ion doping concentration was 1 mol%.

[0020] See Figure 2 Gain diagram of S+C+L band ultra-wideband gain active fiber example 1, which can realize S+C+L band broadband amplification.

[0021] Example 2:

[0022] See Figure 1 The S+C+L band ultra-wideband gain active fiber was fabricated by introducing Bi and Al ions into a loose layer on a SiO2 deposited on the inner wall of a quartz tube using high-temperature chemical vapor deposition (HTCVD). Then, a large number of Er ions were introduced into the quartz tube and deposited onto the loose layer to form the core layer. F ions were then introduced to cover the core layer as the inner cladding, followed by the introduction of Tm ions to form the inner core layer. Finally, the fiber was drawn into an optical fiber using a high-temperature drawing tower. The fabricated fiber had a core diameter of 8.9 μm and a cladding diameter of 125.4 μm. The Er ion doping concentration was 0.4 mol%, the Tm ion doping concentration was 0.2 mol%, the Bi doping concentration was 0.1 mol%, the F ion doping concentration was 0.05 mol%, and the Al ion doping concentration was 0.5 mol%.

[0023] See Figure 2 Gain diagram of S+C+L band ultra-wideband gain active fiber example 2, which can realize 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 consists of an inner core, an inner cladding, a core, a loose layer, and a cladding, arranged from the inside out. The inner core, inner cladding, core, and loose layer together form the fiber core. The inner core is doped with Tm ions, the inner cladding with F ions, and the core with Er ions. The Er ion doping concentration is controlled within the range of 0.01–4 mol%; the Tm ion doping concentration is controlled within the range of 0.01–2 mol%; and the F ion doping concentration is controlled within the range of 0.01–1 mol%.

2. The S+C+L band ultra-wideband gain active optical fiber according to claim 1, characterized in that: The porous 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 concentration of Bi ions is controlled in the range of 0.01~1.5 mol; the concentration of Al ions is controlled in the range of 0.01~10 mol; and the concentration of P ions is controlled in the range of 0.01~10 mol.

4. The S+C+L band ultra-wideband gain active optical fiber according to claim 2, characterized in that: The core diameter is 4~25 μm, and the cladding diameter is 70~250 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 3-5, 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 a gain greater than 20dB is 1460~1625nm, and the noise figure is less than 5dB for all of them.

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