Scanning wavelength tunable laser for optical fiber sensing

Abstract

The utility model discloses an optical fiber sensing-oriented scanning wavelength tunable laser, which comprises a tunable DFB laser array chip, a passive optical combiner chip, a semiconductor optical amplifier (SOA) and a single-mode optical fiber which are sequentially coupled and connected through waveguides, the waveguides are manufactured by adopting a photon lead bonding technology, the light emitting end of the SOA is provided with an inclined waveguide, and the light emitting end of the SOA is provided with an optical fiber. The angle of the inclined waveguide is 6-16 degrees, and the end face of the inclined waveguide is coated with an anti-reflection AR film. According to the utility model, through a photon lead bonding technology, low-cost high-density hybrid integration among the tunable DFB laser array chip, the passive optical combiner chip and the SOA which are arranged in a low-cost matrix manner is realized, the preparation cost is reduced, and the yield is improved.

Description

Technical Field

[0001] This utility model relates to the field of laser technology, and in particular to a scanning wavelength tunable laser for fiber optic sensing. Background Technology

[0002] Fiber Bragg grating (FBG) sensing technology enables sensitive responses and accurate measurements of temperature and strain, finding important applications in numerous fields such as industrial production, bridge construction, and biomedicine. Compared to electrical sensors, FBG sensing allows for compact serial multiplexing, offering greater flexibility and lower cost in applications with limited space. Optical sensors are unaffected by electromagnetic interference, enabling applications in various complex and specialized environments. Currently, the main cost of FBG sensing systems stems from the light source, highlighting the urgent need for low-cost, wide-tunable, and highly integrated laser light sources. Monolithically integrated semiconductor tunable laser light sources require stringent material etching and growth techniques, resulting in higher overall device costs and lower yield rates. Utility Model Content

[0003] Purpose of the utility model: The purpose of this utility model is to provide a low-cost hybrid integrated scanning wavelength tunable laser for fiber optic sensing, which is implemented using photonic wire bonding technology.

[0004] Technical solution: The scanning wavelength tunable laser for fiber optic sensing described in this utility model includes a tunable DFB laser array chip, a passive optical combiner chip, a semiconductor optical amplifier (SOA), and a single-mode optical fiber, which are sequentially coupled through waveguides. The waveguides are fabricated using photonic wire bonding technology. The output end of the SOA is provided with a tilted waveguide with an angle of 6° to 16°, and the end face is coated with an anti-reflective AR coating.

[0005] SOA is mainly used to compensate for the insertion loss caused by passive optical combiner chips. The output end of SOA is equipped with a tilted waveguide with an angle of 6° to 16°, and the end face is coated with an anti-reflective AR coating. The reflectivity is generally set to be less than 0.1% to prevent multi-mode lasing.

[0006] Furthermore, the passive optical combiner chip is a cascaded Y-waveguide or multimode interference coupler (MMI) structure. The passive optical combiner chip is fabricated using one of the following material systems: silicon, silicon nitride, or silicon dioxide. It combines light of different wavelengths emitted from each waveguide of the tunable laser array chip into a single waveguide output.

[0007] Furthermore, each laser unit of the tunable DFB laser array chip is fabricated using reconstructed equivalent chirp technology, introducing an equivalent phase shift or equivalent chirp, or both, into the resonant cavity. The tunable laser array chip is fabricated using reconstructed equivalent chirp technology, utilizing +1 or -1 order gratings for equivalence, introducing an equivalent π phase shift into the resonant cavity. The different operating wavelengths of each laser are achieved solely by designing different sampling periods.

[0008] Furthermore, the waveguide between the SOA and the single-mode fiber is coupled using photonic wire bonding or a lens method.

[0009] Furthermore, the wavelength spacing between the lasers in the tunable DFB laser array chip (1) is 0.6 nm to 4 nm.

[0010] Furthermore, the lasers in each row of the tunable DFB laser array chip are connected by waveguides. The end faces of the waveguides are coated with AR film, with a reflectivity typically less than 0.1%, ensuring single-mode operation of each laser. Lasers with adjacent wavelengths are distributed on different waveguides, with shorter wavelength lasers located closer to the optical output end of the tunable DFB laser array chip. When a laser on the same waveguide away from the optical output end face is operating, a transparent current needs to be applied to the lasers through which its emitted light passes. When applied to a fiber optic grating sensing system, wavelength scanning can be performed on a single laser or on multiple lasers simultaneously.

[0011] Furthermore, the tunable DFB laser array chip, passive optical combiner chip, and SOA are mounted on the same tungsten-copper carrier. The shape of the tungsten-copper carrier compensates for the height difference between the chips, ensuring that all waveguides are at almost the same height, typically requiring a height difference of less than 60 μm. The horizontal alignment error of the waveguides between chips is generally required to be less than 20 μm, and the chip spacing is controlled between 250-270 μm. The mounting process can be performed manually with the assistance of a CCD with micron-level precision, without relying on complex high-precision alignment devices.

[0012] Furthermore, a TEC temperature control module is provided below the tunable DFB laser array chip, which uses independent temperature control for wavelength tuning.

[0013] Beneficial Effects: Compared with the prior art, this utility model has the following advantages: 1. This utility model achieves low-cost, high-density hybrid integration between low-cost matrix-arranged tunable DFB laser array chips, passive optical combiner chips, and semiconductor optical amplifiers (SOAs) through photonic wire bonding technology, controlling the coupling loss between chips to 1-2dB, reducing manufacturing costs, and improving yield; 2. The structure of this utility model allows for larger alignment errors without affecting coupling efficiency, and the photonic wire bonding technology does not significantly increase the processing difficulty for coupling between multiple channels as the number of channels increases; 3. This utility model is applicable to fiber optic gratings or MEMS fiber optic sensing systems, and can significantly reduce the overall system cost. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of this utility model;

[0015] Figure 2 This is a schematic diagram of the structure of a tunable DFB laser array chip;

[0016] Figure 3 This is a schematic diagram showing the mounting of a tunable DFB laser array chip, a passive optical combiner chip, a semiconductor optical amplifier (SOA), and a single-mode optical fiber onto the same tungsten-copper carrier. Detailed Implementation

[0017] The technical solution of this utility model will be further described below with reference to the accompanying drawings.

[0018] The scanning wavelength tunable laser for fiber optic sensing described in this invention includes a tunable DFB laser array chip 1, a passive optical combiner chip 2, an SOA 3, and a single-mode fiber 4, which are sequentially coupled through a waveguide 5. The waveguide 5 is fabricated using photonic wire bonding technology. The output end of the SOA is provided with a tilted waveguide with an angle of 6° to 16°, and the end face is coated with an anti-reflective AR coating.

[0019] The M×N tunable DFB laser array chip 1 is fabricated at low cost using reconfiguration equivalent chirp technology. An equivalent π phase shift is introduced in the +1st-order sub-grating, and both end faces are coated with an AR film with a reflectivity of 0.1% to ensure single-mode laser operation. The tunable DFB laser array chip 1 has M waveguides, with typical waveguide spacing of 127 μm or 250 μm. Each waveguide has N lasers, each designed with a different wavelength, achieved by changing the sampling period. Lasers with similar wavelengths are distributed across different waveguides, while for lasers on the same waveguide, those with shorter operating wavelengths are closer to the output end. When a laser on the same waveguide is far from the output end, a transparent current needs to be applied to the lasers it passes through. Taking an 8×3 tunable DFB laser array chip as an example, there are 8 waveguides with a waveguide spacing of 127 μm. Each waveguide has 3 lasers with a wavelength spacing of 1.6 nm. The distribution of operating wavelengths is as follows: Figure 2 As shown, where λ1 < λ2 < … < λ24. An independent TEC temperature control module 7 is located below the array chip. Each laser can achieve continuous wavelength tuning within a 1.6nm range through thermal tuning, thus enabling the entire tunable laser array chip to achieve continuous wavelength tuning within the 1529.16-1567.13nm wavelength range, covering all 96 channels of the entire C-band and the 50GHz spacing required by the DWDM system.

[0020] Furthermore, the waveguide between the SOA and the single-mode fiber can be replaced with a lens 6.

[0021] The passive optical combiner chip 2 employs a wavelength-selective M×1 cascaded Y-waveguide structure or MMI structure to couple different wavelengths of light emitted from the 1M waveguides of the tunable DFB laser array chip to a single waveguide output. The passive optical combiner chip 2 can be fabricated using materials such as silicon, silicon nitride, and silicon dioxide. For an 8×3 tunable laser array chip, the passive optical combiner chip 2 can be a commercially available chip based on silicon dioxide waveguides, with an 8×1 cascaded Y-waveguide structure. The input waveguide spacing is 127μm, corresponding to the laser waveguide spacing, and the chip's insertion loss is approximately 10dB.

[0022] The function of the SOA is to amplify the signal at the chip output, mainly compensating for the approximately 10dB loss caused by the combiner. The optical output waveguide of the SOA is tilted from 6° to 16°, and the end face is coated with an AR film with a reflectivity of 0.1% to avoid multi-mode lasing caused by end face reflection.

[0023] The tunable DFB laser array chip, passive optical combiner chip, and SOA are mounted on the same tungsten-copper carrier 8. The shape of the tungsten-copper carrier compensates for the height difference between the chips, ensuring that all waveguides are at almost the same height, typically requiring a height difference of less than 60 μm. The horizontal alignment error of the waveguides between chips is generally required to be less than 20 μm, and the chip spacing is controlled between 250-270 μm. The mounting process can be performed manually with the assistance of a CCD with micron-level precision, without relying on complex high-precision alignment devices, offering high flexibility.

[0024] Low-cost, high-density hybrid integration between chips is achieved through PWB technology. The principle involves using multiphoton exposure to directly write polymer waveguides in 3D to achieve coupling connections between chips. To ensure the stability and mechanical strength of the polymer waveguides, they need to be developed and dried with nitrogen immediately after fabrication, followed by continuous heating at 80-85°C for 1-2 hours. For the low-cost hybrid integrated multi-wavelength tunable laser of this invention, the polymer waveguides fabricated using PWB technology can achieve a coupling loss of 1-2 dB between chips.

Claims

1. A scanning wavelength tunable laser for fiber optic sensing, characterized in that, The device includes a tunable DFB laser array chip (1), a passive optical combiner chip (2), an SOA (3), and a single-mode fiber (4) connected sequentially by waveguides. The waveguides between the tunable DFB laser array chip (1), the passive optical combiner chip (2), and the SOA (3) are bonded by photonic wire bonding (5). The output end of the SOA (3) is provided with a tilted waveguide with an angle of 6°~16° and an anti-reflective AR coating on the end face.

2. The scanning wavelength tunable laser for fiber optic sensing according to claim 1, characterized in that, The passive optical combiner chip (2) is a cascaded Y-waveguide or multimode interference coupler (MMI) structure.

3. The scanning wavelength tunable laser for fiber optic sensing according to claim 1, characterized in that, Each laser unit of the tunable DFB laser array chip is fabricated using reconfiguration equivalent chirp technology, which introduces equivalent phase shift or equivalent chirp, or both, into the resonant cavity.

4. The scanning wavelength tunable laser for fiber optic sensing according to claim 2, characterized in that, Each laser unit of the tunable DFB laser array chip is fabricated using reconfiguration equivalent chirp technology, which introduces equivalent phase shift or equivalent chirp, or both, into the resonant cavity.

5. The scanning wavelength tunable laser for fiber optic sensing according to claim 1, characterized in that, The waveguides between the SOA (3) and the single-mode fiber (4) are coupled by photonic wire bonding (5) or by lens (6).

6. The scanning wavelength tunable laser for fiber optic sensing according to claim 4, characterized in that, The waveguide between the SOA (3) and the single-mode fiber is coupled by photonic wire bonding (5) or by a lens (6).

7. The scanning wavelength tunable laser for fiber optic sensing according to any one of claims 1-6, characterized in that, The wavelength spacing between the lasers in the tunable DFB laser array chip (1) is 0.6nm~4nm.

8. The scanning wavelength tunable laser for fiber optic sensing according to any one of claims 1-6, characterized in that, The lasers in each row of the tunable DFB laser array chip (1) are connected by waveguides, and the end faces of the waveguides are coated with AR. Lasers of adjacent wavelengths are distributed on different waveguides, and the shorter wavelength lasers are closer to the optical output end of the tunable DFB laser array chip (1).

9. The scanning wavelength tunable laser for fiber optic sensing according to any one of claims 1-6, characterized in that, The tunable DFB laser array chip (1), passive optical combiner chip (2) and SOA (3) are mounted on the same tungsten copper carrier, and the height difference between the chips is compensated by the shape of the tungsten copper carrier.

10. The scanning wavelength tunable laser for fiber optic sensing according to claim 1, characterized in that, A TEC temperature control module is located below the tunable DFB laser array chip.

Images