CN105136336A - Fiber air ring chamber temperature sensor based on femto-second laser device - Google Patents

Abstract

The invention provides a fiber air ring chamber temperature sensor based on a femto-second laser device. The temperature sensor is characterized by comprising an incident fiber (1), an air ring chamber structure (2) and an emission fiber (3), wherein two ends of the air ring chamber structure (2) are respectively connected with the incident fiber (1) and the emission fiber (3), and the incident fiber (1), the air ring chamber structure (2) and the emission fiber (3) commonly form an all-fiber Mach-Zehnder interferometer. The fiber air ring chamber temperature sensor has advantages of high sensitivity and micro structure and can be applied to various practical high-temperature measurement processes.

Description

A kind of optical fiber air ring cavity temperature sensor based on femto-second laser

Technical field

The invention provides the optical fiber air ring cavity temperature sensor based on femto-second laser, belong to technical field of optical fiber sensing.

Background technology

Mach-Zehnder interferometer is widely used in sensory field, and it uses two-beam interference principle to be made.Traditional Mach-Zehnder interferometer needs the single-mode fiber that two length is identical, is easily subject to the impact as other physical quantitys such as humidity except needing the physical quantity of measurement.As can be seen here, traditional Mach-Zehnder interferometer makes difficulty.So all-fiber Mach-Zehnder interferometer is suggested.Current all-fiber Mach-Zehnder interferometer is mainly based on FBG, LPFG, PCF, and optical fiber vertebral pulling, optical fiber dislocation connection waits Structure composing, although sensitivity is very high, the temperature sensor size that these Mach-Zehnder interferometers are formed is large, is not easy to recycling.In order to solve above problem, a kind of novel all-fiber Mach-Zehnder interferometer is suggested, the making of this temperature sensor has used femto-second laser, femto-second laser is used for accurate micro-nano technology, it is when with matter interaction, can ultrahigh resolution be realized, superhigh precision, thus reach the processing and manufacturing of nanoscale.The Mach-Zehnder interferometer of this all-fiber has highly sensitive, the advantages such as structure is small.

The light originally only transmitted in fibre core is made to carry out transmitting and interfering with the form of core mode and air ring cavity mould respectively based on the air ring cavity configuration in the optical fiber air ring cavity temperature sensor of femto-second laser.When measure to external world by environment temperature for this sensor of use, each temperature that changes all can make interference fringe drift about.This is because air ring cavity mould is different with the responsiveness of core mode to temperature variation, thus causes original optical path difference to change.Along with the change of optical path difference, interference fringe will change to some extent.When temperature is after a series of change, a series of interference fringe corresponded namely can be observed on spectrometer.At some feature locations of interference fringe, such as interference peaks or interference paddy, can see that the wavelength that extreme value is positioned at drifts about, can realize temperature survey by the drift value of monitoring interference spectrum.

Summary of the invention

The object of the present invention is to provide a kind of optical fiber air ring cavity temperature sensor based on femto-second laser.This device can will treat that the variable quantity of testing temperature is converted into the wavelength shift of detectable signal.Have high sensitivity, structure is small, is easy to advantages such as reusing.

The present invention is achieved through the following technical solutions:

Based on an optical fiber air ring cavity temperature sensor for femto-second laser, be made up of incident optical (1), air ring cavity configuration (2), outgoing optical fiber (3); The two ends of air ring cavity configuration (2) are connected with outgoing optical fiber (3) with incident optical (1) respectively; Incident optical (1) and air ring cavity configuration (2) form all-fiber Mach-Zehnder interferometer jointly with outgoing optical fiber (3).

Described a kind of optical fiber air ring cavity temperature sensor based on femto-second laser, it is characterized in that: incident optical (1), outgoing optical fiber (3) all can adopt G.652 single-mode fiber, incident optical (1) and outgoing optical fiber (5) length are 20 ~ 40cm.

Described a kind of optical fiber air ring cavity temperature sensor based on femto-second laser, it is characterized in that: the optical fiber that air ring cavity configuration (2) uses is for can adopt G.652 single-mode fiber, length is 50um ~ 100um, the ring cavity exradius of air ring cavity configuration (2) is 4um ~ 7um, and inner circle radius is 2um ~ 5um.

Principle of work of the present invention is: the light sent when wideband light source arrives air ring cavity, because the core diameter of incident optical is thicker than the core diameter of this section of optical fiber of air ring cavity configuration through incident optical.The light that such script transmits in fibre core is divided into two parts, some light enters in air ring cavity, another part light will continue to transmit along fibre core, when arriving air ring cavity configuration terminal, the light transmitted in air ring cavity interferes with the light transmitted in fibre core, eventually passes outgoing optical fiber and arrives spectrometer.

The light wherein transmitted between fibre core and air ring cavity there occurs interference, and briefly, the interference between fibre core and air ring cavity can obtain with known formula:

Wherein I _coreand I _cavitybe the light intensity spreading out of light from fibre core and air ring cavity configuration respectively, λ is lambda1-wavelength, and L is the length of air ring cavity, that effective refractive index between core mode and air ring cavity mould is poor, it is the initial phase of interfering.Because L is constant, so the formula of the temperature control of this Mach-Zehnder interferometer is

$\frac{\mathrm{d\λ}}{\mathrm{dT}}=\frac{\mathrm{\λ}}{n_{\mathrm{eff}}^{\mathrm{core}}\left(T\right)-n_{\mathrm{eff}}^{\mathrm{cavity}}\left(T\right)}(\frac{{\mathrm{dn}}_{\mathrm{eff}}^{\mathrm{core}}\left(T\right)}{\mathrm{dT}}-\frac{{\mathrm{dn}}_{\mathrm{eff}}^{\mathrm{cavity}}\left(T\right)}{\mathrm{dT}})$

Wherein with be the temperature coefficient of fibre core and air dielectric refractive index respectively, at different temperature, the effective refractive index of air ring cavity remains unchanged, and therefore the temperature coefficient of fiber core refractive index determines the temperature control of Mach-Zehnder interferometer.

When measure to external world by temperature for this sensor of use, each change ambient temperature, because air ring cavity mould is different with the responsiveness of core mode to temperature, the optical path difference of air ring cavity mould and core mode is changed, thus the phase differential changed between air ring cavity mould and core mode, interference fringe is drifted about, and can reduce measured signal by monitoring interference spectrum wavelength shift.

The invention has the beneficial effects as follows: based on connecting in air ring cavity configuration, Mach-Zehnder interferometer is made this temperature sensor.The light transmitted in fibre core is divided into two parts, and a part of light enters air ring cavity, and the fibre core continued along scaling loss transmits by another part light, and when arriving air ring cavity configuration terminal, the light transmitted in air ring cavity interferes with the light transmitted in fibre core.When changing the ambient temperature of sensor, corresponding interference spectrum will drift about.The Mach-Zehnder interferometer that this sensor connects in adopting, stability is better, and sensitivity is higher, and is not vulnerable to the impact of extraneous variations in refractive index.

Accompanying drawing explanation

Fig. 1 is the optical fiber air ring cavity temperature sensor schematic diagram based on femto-second laser of the present invention;

Embodiment

Below in conjunction with accompanying drawing and embodiment, the invention will be further described:

See accompanying drawing 1, a kind of optical fiber air ring cavity temperature sensor based on femto-second laser, is made up of incident optical (1), air ring cavity configuration (2), outgoing optical fiber (3); The two ends of air ring cavity configuration (2) are connected with outgoing optical fiber (3) with incident optical (1) respectively; Incident optical (1) forms all-fiber Mach-Zehnder interferometer with air ring cavity configuration (2) and outgoing optical fiber (3).The manufacturing process of air ring cavity configuration (2) is as follows: punch at fiber end face with femto-second laser, laser spot diameter is transferred to about 2um, makes a call to a circle aperture, have intersection between each aperture in covering along fibre core.Regulate simultaneously the intensity of femto-second laser and focus point far and near thus control the degree of depth of aperture.Therefore, annular air chamber is formed at fibre core and cladding interface place.After having beaten hole, because the inside surface in annular air chamber is smooth not, so use HF to corrode optical fiber, make it level and smooth.Then the end face of air ring cavity configuration (2) is connected with outgoing optical fiber (3) with incident optical (1) respectively.

The working method of apparatus of the present invention is: by a termination wideband light source of temperature sensor, another termination spectrometer.When the light that wideband light source sends arrives air ring cavity configuration through incident optical, originally the light transmitted in fibre core is divided into two parts, a part enters air ring cavity, another part light will continue to transmit along fibre core, when arriving air ring cavity configuration terminal, the light propagated in air ring cavity interferes with the light transmitted in scaling loss fibre core.When changing the ambient temperature of sensor, corresponding interference spectrum will drift about, thus can draw the sensitivity of this sensor.

Claims (3)

1. the invention provides a kind of optical fiber air ring cavity temperature sensor based on femto-second laser, it is characterized in that: be made up of incident optical (1), air ring cavity configuration (2), outgoing optical fiber (3); The two ends of air ring cavity configuration (2) are connected with outgoing optical fiber (3) with incident optical (1) respectively; Incident optical (1) forms all-fiber Mach-Zehnder interferometer jointly with air ring cavity configuration (2) and outgoing optical fiber (3).

2. a kind of optical fiber air ring cavity temperature sensor based on femto-second laser according to claim 1, it is characterized in that: incident optical (1), outgoing optical fiber (3) all can adopt G.652 single-mode fiber, incident optical (1) and outgoing optical fiber (3) length are 20 ~ 40cm.

3. a kind of optical fiber air ring cavity temperature sensor based on femto-second laser according to claim 1, it is characterized in that: the optical fiber that air ring cavity configuration (2) uses can adopt G.652 single-mode fiber, length is 50um ~ 100um, the ring cavity exradius of air ring cavity configuration (2) is 4um ~ 7um, and inner circle radius is 2um ~ 5um.