工学部SSSVプログラム
日中共同セミナー(２０１２年９月１９日―９月２７日)

Researches on the micro-structured fiber gratings
and their applications to high sensitive fiber sensors
and all-optical signal processing devices

Hongpu Li
Faculty of Engineering, Shizuoka University, 3-5-1, Johoku, Hamamatsu,
432-8561, Japan

ABSTRACTz

Calibration of a phase-shift formed in a linearly chirped fiber Bragg grating byusing wavelength-interrogated fiber ring laser and its application to temperature
sensorz

Cladding mode coupling in a wide-band fiber Bragg grating and its application toa power-interrogated temperature sensorz

Phase shifted and cascaded long-period fiber grating written by using focusedhigh-repetition-rate CO2 laser pulseszLong period fiber grating and its application to all-optical pulse shapingz

Fabrication of micro/nano fiber by using focused high-repetition-rate CO2 laser
pulsesInvestigation of the phase-shift formed in a linearly chirped fiber Bragg gratingby using power-interrogated fiber ring laser
Lunlun Xian1 and Hongpu Li2
Graduate School of Science and Technology, Department of Electrical and Electronic Engineering, Faculty of Engineering,
Shizuoka University, Johoku 3-5-1, Hamamatsu, 432-8561, Japan

1

2

1. Introduction
Phase-shifted fiber Bragg grating (FBG) has been comprehensively studied and widely used in the fields such as the fiber lasers, DWDM filter, etc. [1, 2]. However until present, quantitative analyses on the calibration of the resulted phase-shift and a
relationship between the transmission (strength) of the resulted
notch filter and the amount of the phase-shift have rarely been
given at all. In this paper, relationship between the phase-shift
and the strength of the resulted narrow filter is theoretical andexperimental demonstrated. Furthermore, a novel scheme which
is based on the utilization of a power–interrogated fiber ring laser
working for the calibration of the induced phase-shift is experimentally demonstrated.
Fig.2. Experimental setup for the SLM EDF ring laser.

2. Experimental setup and results
It is found that there existed a beautiful one-by-one relation between amount of the inserted phase-shift and the transmission of
the resulted band-pass filter in theoretical analysis, although it isnonlinear one. Here we perform the experimental tests for a linearly chirped FBG (provided by TeraXion Inc.) with different
amounts of the phase shift introduced by a PZT, which is shownin Fig.1 Characteristics for this utilized grating have been described in details in [2]. The transmission magnitude increases inaccordance with the PZT voltages, it reaches the maximum when
the applied voltage is about 160V corresponding to the casewhere  phase shift is originated.
The one-by-one relationship between the transmission of thenarrow band-pass filter and the phase-shift induced in the FBG
means that one can indirectly know the amount of the phase shift
in a FBG induced by PZT once the transmission of the band-passfilter is precisely measured. To verify the proposal, an Erbiumdoped-fiber (EDF)-based fiber ring laser capable of working at
single-longitude-mode (SLM) is utilized here. Figure 2 shows theschematic diagram of the experimental setup. In this experiment,
the 980nm-LD pump power is kept as a constant of 100 mW. In
order to show well the dependent of the laser output on the PZT
voltage, we summarized all the data and redraw them in Fig. 3.
After the interpolate operation to the data shown in Figs. 1-3, It
is easy to find the one-by-one relationship between the laser output power and the induced phase-shift in the FBG, which isshown in Fig. 4.

Laser power (W)

4.0
Exp. data
Poly. fit

3.0
2.0
1.0
0.0
30

60

90

120

150

180

PZT Voltage (V)Fig.3. Dependent of the laser output power on the amountof the voltage applied on PZT.

Laser power (W)

4.0Interpolated curve

3.0
2.0
1.0
0.0
1.0

2.0

3.0

Phase shift (radian)Transmission

1.0

30V
40V
70V
100V
130V
160V

0.8
0.6
0.4
0.2
0.0
1537.01537.21537.41537.6

Wavelength (nm)Fig.1. Measurement results for the spectra of the narrow
band-pass filter while different PZT voltages are applied.

Fig.4. Dependent of the laser power on the amount of thephase shift induced in the FBG.

3. Conclusion
The relationship between the amount of the induced phase-shift
in a linearly chirped FBG and reflection of the resulted narrow
bandpass filter is theoretical and experimental demonstrated. A
novel scheme based on the utilization of a power–interrogatedfiber ring laser for quantitative calibration of a phase-shift isnumerically and experimentally demonstrated.

References
1.
2.

M. Guy, et al., Electron. Lett., vol. 31, 1924-1925 (1995).
X. Chen, et al., J. Lightw. Technol., 28, 2017–2022 (2010).

Fabrication and characterization of micro-ring optical resonator based on As2Se3 glass
Masahiro Fukuyo1 and Kazuhiko Ogusu2
Graduate School of Science and Technology, 2Department of Electrical and Electronic Engineering, Faculty of Engineering,
Shizuoka University, Johoku 3-5-1, Hamamatsu, 432-8561, Japan1

1. Introduction
Optical fiber technology is used, such as Silicon as how tosend information to the recent large capacity has been widelyused, it has become essential to modern technology. On the other
hand, in that require improvement in signal processing speed dueto the large capacity of information, the signal processing by theelectrical signal is limits at 10Gbit / s, the signal processing by
light, the transmission rate of more of the all optical device thatis take advantage has been attracting attention. All-optical devices are required to be low-loss communication wavelength bandand high nonlinearity. In this research, we fabricated micro-ringresonator using As2Se3 glass, check the bistable operation.
Fig.2. Micro-ring resonator structure.

2. Fabrication for As2Se3 waveguides

The waveguide structure is fabricated waveguide layer based
the Ag-As2Se3, as shown in Fig.1. This waveguide was tuned
wavelength in 1.064µm. This waveguide is composed of thesubstrate is silicon wafer, the lower cladding layer is PMMA, thewaveguide layer is Ag-As2Se3 and the strip layer is As2Se3. Then,
thickness of the waveguide layer d is 0.40μm, thickness of the
strip h is 0.05μm and waveguide width w is 2.0μm.The fabrication process of the waveguide has eight steps. The first step is
Silicon Wafer coated with PMMA. The second and third step isdeposited As2Se3 and Ag. The fourth step is Ag-As2Se3 was fabrication by photo-doping. The fifth step is it coated with OFPR.
The sixth step is the pattern exposed to the sample. The seventh
step is deposit As2Se3 again. The last step is Lift off OFPR. Fig.2
is micro-ring resonator structure. We depicted the eighteen types
of waveguide to a sample. Coupling unit interval D is 1.0, 1.5,
and 2.0μm. Length of the coupling Lc is 4, 5, 6, 7, 8, and 9μm.
Radius of ring R is 100μm.

3. Experimental setup and results

Fig.3. Experimental system for the measurement of
the resonance characteristics.

The experimental setup for measurement of the ring resonator
is shown in Fig.3, where the input light is generated by tunable
laser, which is varied 1063 to 1065. It gets through beam splitterand half-wave plate, and focused by 60 times lens. Fig4 is spectral response of ring resonator. Resonance wavelength interval
was 0.38nm, 0.34nm and 0.37nm.The resonant depth was about
3dBm to 1dBm.

Fig.4. Measurement results for spectral response ofring resonator.

4. Conclusion

Fig.1. Waveguide structure.

We were able to establish the fabrication technology of the ring
resonator to measure the transmitted power. Resonate characteristics, depth of the resonance of up to 3dBm. Cause of many
variations of the measurement was considered to be not only thefundamental mode propagating and other modes.

Fabrication of a long-period fiber grating by using CO2 laser
Keisuke Hishiki
Department of Electronic Engineering, Shizuoka University
mode is1. Introduction
Recently, device which used optical fiber are studied for taking much notice of many applications. For example, longperiod fiber gratings (LPG), fiber Bragg grating (FBG), nanofiber, and so on. The phase-shifted long fiber (PSLPG) is inserted the shift in LPG. Above all, LPG and PSLPG have many
applications, such as band reject filters, gain spectrum flattening filter and temperature sensor, pulse shaping device respectively. So, LPG has been already studied and has been succeed
to fabricate by expose photosensitive fiber to ultraviolet. However, it is not yet about general fiber. In this study, LPG is fabricated by irradiate general fiber with CO2 laser.

coupled with core mode again. So, this works to look like MachZehnder interferometer.
The wavelength of LPGs is satisfied with λ=(ncore-nclad)Λ whensolve phase matching condition, where ncore and nclad is effective
refractive index of the fiber core and that of clad, respectively. In
this study, I think three typical types, LPG, PSLPG, and CLPG
as follow. I use the single mode fiber have ncore=1.455 and nclad =1.453. So, whenλequal to 1550nm , Λ= 630μm. Therefore, weapply to this value for simulation and experiment in all LPGs. In
CLPGs, peak wavelength difference are satisfied with ∆λ=λ2/(ncore-nclad) d . The smaller ∆λ is, the better sensitivity.

2. Experimental setup
The experimental setup is shown in figure 1.The CO2 laser
beam through the shutter is reflected by the mirror on the stage
and focus the beam on the fiber by a spherical lens. The fiber isclamped the fiber alignment stage. To measure the transmission
spectrum of the LPG, the fiber is connected between an amplified spontaneous emission (ASE) and an optical spectrum analyzer (OSA). Exposing the fiber to the CO2 laser, refractive index
of the fiber core change (increase) for producing the stress In
order to realize a periodic refractive index structure, the shutter ispossible on/off and the stage is available to move, they are controlled by Lab-view (PC soft). The CO2 laser works at a typicalfrequency of 5kHz and duty-cycle is changeable between 0% and95%. The beam is focused though the spherical lens with a focus
length of 70 cm, the minimum spot size on the fiber is about 100μm .

Fig.1 Measured spectral of LPGs

Fig.2 Measured spectral of PSLPGs for πshift and π/2 shift

Fig.1 experimental setup

Fig.3 Measured spectral of CLPGs for d=10.6cm and 37.1cm

3. Principle
LPG has a periodic effective refractive index change of the fiber core. Its characteristics have the loss peak in specific wavelength when we input the light having normalized intensity. And
PS-LPGs have also this characteristic, but it differs from LPGs in
terms of being divided the wavelength. These spectral arechanged by the distance which I insert. Two cases are consideredby the distance inserted. PSLPG is when the inserted distance isshorter than grating period(Λ), and cascaded long period fiber
grating (CLPG) is when the inserted distance is much larger
than Λ. These LPGs is generated mode coupling to as two grating connected in series. In the principle of these LPGs, coremode is coupled with cladding mode for the first grating edge, it
propagates directly in no grating area, the generated cladding

4. Conclusions
Three kinds of LPGs have been successfully fabricated by using
the CO2 laser from Fig.1 to Fig.3. It is found that characteristics
of PSLPG and CLPG spectral strongly depend on the magnitudeof the inserted phase shift in a LPG. You can see that the wavelength of LPGs rely on the grating period from Fig.1 left. Resonant wavelength of all LPGs slightly increases the period because of applying the strain to the fiber. In Fig.3 characteristics
change by the distance (d).
Reference[1] Y. J. Rao, et al., Opt. Communications, 229, 209 (2004).
[2] R. Slavik, et al., Opt. Express, 14 , 10699 (2006).
[3] H. Ke et al., IEEE Photon. Techn. Lett. 19, 1596 (1998).

Optical bistability in a Fabry-Perot resonator using a nonlinear fiber
Yuki Iwamuro and Kazuhiko Ogusu
Graduate School of Science and Technology, 2Department of Electrical and Electronic Engineering, Faculty of Engineering,
Shizuoka University, Johoku 3-5-1, Hamamatsu, 432-8561, Japan

1.

Introduction

dependent of the characteristic on change of the initial detuning.

When a high density power enters the medium which has highWhen the initial detuning is -0.2π, we can obtain the good bistability,

nonlinearity, the individual input-output characteristic can be

and the initial detuning is -0.4π, the characteristic is linear.

obtained. This characteristic is called the optical bistability. It has two
stable states by one input. And it can be obtained the limiting
characteristic or differential amplify characteristic if change theconditions. We can apply these characteristics to optical switch, linear
amplifier, or optical power limiter.

These devices are called all

optical devices, which can realize the very fast operating device.
In this paper, we investigate the optical bistability using a As2S3 fiber(a)Fabry-Perot resonator numerically and experimental setup.

2.

(b)Fig.1 Input-output characteristic

Modeling for the Fabry-Perot resonator

Fabry-Perot resonator is constructed by a medium and two mirrors.

3.

Experimental setup

This resonator can be constructed only put the medium between

Fig. 2 is the experimental setup for observing optical bistability.

mirrors. This resonator needs the mirror which has high reflectivity.

The light source is the laser which generates the pulse its width isIn this study, we make the mirrors dielectric multilayer [1] on the

500ps and repetition rate is 10Hz at the 1.064μm. In order to getedge of the fiber by vacuum evaporation. In order to get a reflectivity

the detuning, one mirror is made on the edge of the SiO2 single

over 90% and the wavelength which is peak of the reflectivity ismode fiber at the side of the input and the other mirror is made on

around 1060nm, we use the materials of the multilayer are ZnS

the edge of the As2S3 fiber which can be moved by the actuator at(refractive index is 2.32) and MgF2 (refractive index is 1.38). The

the side of the output.

thickness of the each layer are 91.7nm (ZnS) and 154.2nm (MgF2)
respectively, the number of layer is 7.
In the Fabry-Perot resonator, the output field Eout(t) is given by
E

t

TE

RE

t

t

t R exp

jφ

φNF t

tR

2t R exp

j 2φ

φNF t

tR

φNB t

2t R
(1)

where t R

nL/c is the cavity transit time, R (=r2) is the reflectivityof the mirror, T (=1-R) is transmissivity of the mirror, φthe linear phase shift, φNF t

t R and φNB t

2t R

nk L isFig.2 Experimental setup for observing optical bistability

are thenonlinear phase shifts of the forward and backward propagating

4.

wave in the medium, respectively, given by

Optical bistability in the As2S3 fiber Fabty-Perot resonator has been

φNF t

tR

φNB t

2t R

L
T
L
T

1

R |E

t |

R|E

t

2t R |

(2)

|E

t |

1

R |E

t

2t R |(3)

Conclusions

numerically investigated. In order to realize the optical bistability, wemust make the mirror with more high reflectivity mirror. So we must
adjust the layer thickness of multilayer and make the mirror moreclearly.

where k is the wave number, η is the wave impedance in thevacuum, n2 is the nonlinear refractive index of the medium [2]. The

References

result of the calculation for optical bistability is shown in Fig. 1. In[1] S. J. Orfanidis “Electromagneti c waves and Antennas”,(2008)

Fig.1 (a), the optical bistability is obtained when the cavity length is[2] K.Ogusu, et al Jpn. J. Appl. Phys. Vol. 42 pp. 434-438 (2003)

1mm, reflectivity of the mirror is 90%, initial detuning is -0.1π, input
pulse width is 0.5ns, and input power is 1mW. Fig.1 (b) shows theCladding mode coupling in a wide-band fiber Bragg grating and its application to a
power-interrogated temperature sensor
Peng Wang and Hongpu Li
Introduction

thermal responsibility is about 0.01626dB/0C Moreover,

Investigations for the cladding mode influence on theunlike most the FBG-based sensors reported before [1-2],

spectrum of a linearly chirped FBG with bandwidth larger thanhere the utilized FBG is functioned simultaneously as

10 nm, based on the cladding-mode coupling phenomenon, aboth the sensing and the interrogating element.

1.

novel FBG-based all-fiber sensor enabling to measuretemperature within the range of 17-180

1.00

o

C is firstly proposed

technique instead of the spectrum-shift measurement with a
optical spectrum analyzer (OSA)

2.

0.75

Reflection

and successfully demonstrated by using power-interrogation

T=17 0 C
T=101 0 C
T=181 0 C

0.50
0.25
0.00
1530

Principle and experimental setup

1535

1540

1545

W avelength (nm )We perform various investigations to the temperature
performance of the setup shown in Fig. 1, where the FBG isFig. 2. The reflection spectra of the utilized LCFBG atlocated in a temperature chamber and the temperature canthree different temperatures, 17, 101, and 180

changedbetween170C

to1800C.

1

Exp. Data
Linear fit

0
-1
-2

0

50

100

150

200

Temperature (oC)Fig. 1. Experimental setup for the temperature measurement
based on the power-interrogated method.

Fig. 3.

Measurement results for the dependence of theoutput power vs. the temperature

The results are shown in Fig. 2. It can be seen that the as thetemperature is increased, the spectra is right shift with a thermalC,

respectively

Output power (dBm)bediscretely

03.

Conclusion

responsibility about 10.85 pm/0C, which is nearly the same

Based on this phenomenon, a novel FBG-based sensor

quantity as those reported before. To guarantee the setup (shownenabling to measure temperature in the range of 17-1810C isin Fig. 1) works in a linear region corresponding to thefirstly demonstrated just by using a power-interrogation

wavelength in the range of 1537.5 nm to 1540.6 nm as is shownin Fig. 2, the working wavelength of the DFB laser is fixed and
set in advance as 1540.60 nm. Figure 3 shows the measuring
results for the change of the output power (PD) vs. temperaturechange. It can be seen that as expected, almost a fine linear

technique. Unlike most of the previous FBG-based sensors,
here the utilized FBG is functioned as both the sensing andinterrogating element, which considerably simplifies thesensing system and make it more compact and the least cost.

References[1]

W. W. Morey, et al. SPIE Fiber Optic & Laser Sensors VII, 1169，

relationship between the laser power at the port of PD and the(1989)

ambient temperature of the grating has been obtained and the[2]

S. M. Melle , et al. IEEE Photon. Technol. Lett., 516–518(1992).

Fabrication of Cylindrical Opals and Inverse Opals and Their Optical Properties
Chen Wei
Wang Ming(Key Laboratory on Opto-Electronic Technology of Jiangsu Province, School of Physics Science and Technology, Nanjing Normal
University, Nanjing 210046, China)

1. Introduction
Microstructure optical fibers (MOFs) have exhibited many
novel optical properties in recent years. Photonic band gap fibers(PBGFs) with hollow core guiding structures are a kind of
microstructure optical fibers (MOFs) to overcome the limitationsof traditional silica optical fibers. Many efforts have been madeto fabricate 3DPBGFs: E. Valdivia et al. coated a standard opticalfiber with three dimensional colloidal crystals which could be
used as a template to form inverse opal hollow core PBGFs[1];S.-M. Yang et al. created polymer hollow cylindrical structureswith three dimensionally interconnected air cavities byinfiltrating polymer precursor into a colloidal crystal template on
fibers which was fabricated by dip-coating method[2].

Fig1.Fabrication schematic diagram

2. Experimental setup and results
Capillaries were cleaned in an ultrasonic bath fist using
acetone and then deionized (DI) water for 10 minutes
respectively. Then cleaned capillaries were dried with nitrogen
before use. To fabricate opals on the internal surface ofcapillaries, PS colloidal solution dispersed in DI water withconcentration of ~1vol % was injected into a capillary. The
height of the solution inside the capillary is 10-95mm and can be
precisely controlled by a micro-pump. One end of the capillary
was sealed to control the evaporation direction of solvent. Fig1(a) shows a schematic diagram of fabrication opals on a capillaryinternal wall and Fig1 (b) is a schematic diagram of colloidal
crystal growth on a capillary internal wall with verticaldeposition method. Fig1 (c) is cross section view the capillaryinternal wall coated with opals. Fig2 is schematic diagram oftransmission spectrum measurement. Transmission spectrum wasmeasured with a YOKOGAWA optical spectral analyzer(AQ6370). The YOKOGAWA white light source (AQ4305) was
coupled into a multimode optical fiber and focused to inverse
opals at normal incidence with a couple of collimating lens.
Transmitted lights were focused to the optical spectral analyzer
by a lens.
Fig3 (a)~(d) are images of opals on the internal wall of acapillary assembled from 490nm PS microspheres. (a) and (b)are optical microscope images observed in reflection mode, (c)are SEM images of opals on the internal wall of a capillary, inset
is high magnification of internal wall，(d) top cross section
surface of the opals inside a capillary and inset is highmagnification of the cross section.(e)~(h) are images of 490nm
silica inverse opals on the internal wall of a capillary with sol-gel
co-assembly method. (e) are bare capillary and internal wallcoated with composite colloidal crystal, (f) internal wall
preserved with silica inverse opals after sintering and barecapillary. The axial uniformity together with the symmetric color
distribution on the capillary internal edges attests to the highquality of composite colloidal crystal, which spectrally shifts thestop band with the viewing angle around the capillary curved
surface. The color on the internal edge of the capillary has a blue
shift after removing the PS colloidal crystal template as theeffective refraction index decreased. (g) longitudinal section of
the capillary whose internal wall coated with silica inverse opals,
inset is high magnification of internal wall. In the inset uniform
small pores on the bottom of the big pores can be seen obviously
which show the good connectivity of the air spheres.(h) crosssection of inverse opals and the high magnification of the crosssection.

Fig2 Schematic diagram of transmission spectrum measurement

Fig3. Images of opals on the internal wall of a capillary assembled
from 490nm PS microspheres

3. Conclusion
Hollow cylindrical opals and inverse opals have been made by
self-assembly method in a capillary. With vertical self-assembly
method hollow cylindrical PS opals and SiO2 inverse opals filmsof different radiuses have been made in capillaries with sameradiuses. According to microstructures and optical performanceof fabricated samples, radius of curvature basal and diameter ofmicrospheres used are main factors affect the film structure andoptical performance. The complete solution states change havebeen discussed. Scanning electron microscope is used tocharacter its internal structures.

References[1] J. Li, et al., Opt. Express 13, 6454-6459 (2005),[2] J. H .Moon et al., Journal of Colloid and Interface Science 287,
173-177 (2005).

The design and simulation of the accelerometer
You Jingjing and Wang Ming
Key Laboratory on Opto-Electronic Technology of Jiangsu Province, School of Physics Science and Technology,
Nanjing Normal University, Nanjing 210046, China

1. Introduction
The miniature fiber optic sensor based on Fabry-Perot (F-P)
interferometry reported is designed for vibration monitoring
applications. The sensor used for this application is not only
safety and cost economics , but also unaffected to radiation orhigh electromagnetic fields .

2. The structure design of the accelerometer
The designed structure of the accelerometer is composed of
SU8 diaphragm with four beams clamped around and thecommercial fiber. The schematic diagram of the accelerometerand the SU8 diaphragm with four beam around clamped areshown in Fig.1 .The F-P cavity is composed of the terminal faceof the fiber and the subdiaphragmatic surface . SU8 diaphragmhas very excellent imaging characteristics , and it is capable ofproducing very high aspect ratio structures . Commercial fiber isused to transfer incident and reflected light .

From the simulation, we captured a diagram of the maximum
displacement in the z direction caused by the harmonic excitation,
shown in the Fig.3 .The blue curve stands for the displacement of
the fiber terminal surface , and the red curve stands for the
displacement of the subface of the SU8 diaphragm . Therefore ,the difference between the two curves is the length of the F-P
cavity . We can get the changing length of the F-P cavity
30.7369μm , and the response ratio about 100nm/10hz in therange of 0 to 3000 hz .

Fig.2. The modal of the designed structure with a harmonic excitation
loading in the subface of the structure .
Fig.1. The schematic diagram of the accelerometer and the SU8
diaphragm with four beam around clamped .

3. The theory of the accelerometerIn the spring mass system with one degree of freedom loaded
a simple harmonic excitation in the substrate[1], the relative
displacement of the mass is as followed:

(1)
and ,
,is the damping ratio ;,is frequency ratio，which is the ratio of the external
excitation frequency dividing by the natural frequency of thesystem;,w is the natural frequency.
As γ nearly equal to zero , we can get equation(2) ,Fig.3. The maximum displacement of two points in the z direction causedby the harmonic excitation .

5. Conclusion
With the help of polymer MEMS technology, the high aspectratio structure is feasible and realizable. Through our work, thedesign structure can meet the condition of vibration measuring .
However , the vibration measuring is a complicated process, andthe parameter of system is remained to be further determined.

References[1] Jesus M. Corres ,Sensors and Actuators A 132 (2006) 506–515(2)
The value of X is in direct proportion to the acceleration
amplitude .It is the principle of the accelerometer .

4. The simulation of system characterization
A model of the designed structure is established and simulatedby CoventorWare , which is shown in Fig.2 . In the simulation ,asimple harmonic excitation loads in the bottom face of themodal , that can cause the SU8 diaphragm vibrating according to
the theory of the accelerometer.

Measurement of Fiber Length Using Passively Mode Locked Fiber Laser with a Semiconductor Saturable
Absorber Mirror
Congcong Zhang1, Ming Wang2*
1

School of Physical Science and Technology, Jiangsu Key Lab on Opto-Electronic Technology, Nanjing Normal University, Nanjing
210046, P. R. China, 15950562770, 025-83598685
2
School of Physical Science and Technology, Jiangsu Key Lab on Opto-Electronic Technology, Nanjing Normal University, Nanjing
210046, P. R. China, 025-83598685,025-83598685

1. Introduction
This paper investigates the passively mode-locked erbiumdoped ring fiber laser with a semiconductor saturable absorbermirror and its application for measurement in Fiber Length. Using a semiconductor saturable absorber mirror (SESAM), a passively mode-locked fiber ring laser was demonstrated and stablesub-picoseconds pulses were produced. A new method for measuring optical fiber length using an all-fiber mode-locked laser
with the semiconductor saturable absorber mirror was presented.

2. Experimental setup and results
Using a semiconductor saturable absorber mirror (SESAM), a
passively mode-locked fiber ring laser was demonstrated andstable sub-picoseconds pulses were produced. This ring fiber
laser was constructed with a WDM（Wavelength Division Multiplexing）, erbium-doped fiber as gain medium as well as circular, polarization controller, and coupler. In experiments, the fiber
laser operated stably with mode-locked pulse laser output whose
peak wavelength of 1558nm, spectrum width of 7.2 nm without
any satellite pulses or pedestal, repetition frequency of 7.75 MHz
and maximum mean optical power of 2.6 mW. It was found thatthe characteristics of the output laser pulse in time domain wouldchange a little while adjusting the polarization controller in experiments. The pulses was measured by an oscilloscope and afrequency spectrograph, and theoretically the pulses were as
narrow as 347 fs. During long time, the laser can work stable.
The experimental setup was simple, compact, and self-started.
The experimental results are helpful to the use of semiconductor
saturable absorber mirror in passively mode-locked fiber laser.
Optical fiber is the best media in modern communication networks for its characteristics of low loss and wide frequency band.
Precise measurement of optical fiber length is a fundamental
technique in many areas, such as in optical communications andfiber-optic sensing networks. A new method for measuring optical fiber length using an all-fiber mode-locked laser with thesemiconductor saturable absorber mirror was presented. The
semiconductor saturable absorber mirror can act as the saturable
absorber for mode-locking with nonlinear polarization rotation
based on the random birefringence of the single-mode fiber. The
mode-locked fiber laser has the all-fiber nature and can be stable
for a long term. Since the transit time in cavity corresponding to
the fundamental frequency is exactly linearly proportional to thecavity length of the mode-locked fiber laser, a novel simple
method to measure the fiber length has been experimentallydemonstrated using a mode-locked fiber laser configuration.
Compared to presented methods, there is no dead zone in our
method and no limitation in measuring fiber length over hundreds of kilometers due to low insertion loss and direct splicing
into an all-fiber system. First we test single fiber with several
lengths from about 100 orders of magnitude to about several
meters. Then we test the system with many ways. The resultshows our system has a large measurement range and high precision. The experimental setup was simple and easy to test. We
call this as the mode-locking method. It has a high value in practical and can be used in the actual construction as we can see.

Fig.1.Experimental for the passively mode locked
fiber laser

Fig.2. The spectrogram of passively mode locked
fiber laser

3. Conclusion
A passively mode-locked erbium-doped ring fiber laser with asemiconductor saturable absorber mirror is demonstrated in experiment. A new method for measuring optical fiber length using
an all-fiber mode-locked laser with the semiconductor saturable
absorber mirror was presented. It has a high value in practicaland can be used in the actual construction.

References
1.

2.

3.

4.

U Keller;D A B Miller;G D Boyd, Solid-state lowloss intracavity
saturable absorber for Nd:YLF lasers:an antivesonant semiconductor Fabry-Perot saturable absorber, Optics Letters, 1992, Vol. 17(7),pp. 505-507,
De Souza, E.A.: Soccolich, C.E., Saturable absorber modelockedpolarisation maintaining erbium-doped fibre laser, Electronics Letters, 1993, Vol. 29(5), pp. 447-449.
WANG Jing，ZHANG Hong-ming，ZHANG Jun，YAN Meng,YAO Min-yu, Passively Mode-Locked Fiber Laser with a Semiconductor Saturable Absorber Mirro, Chinese Journal of Lasers,
2007(02),
ZHANG Zh X;WU J;XU K, Multiple output states from passivemode-locked fiber lasers, laser technology, 2009(05),Self-mixing interferometer based on sinusoidal phase modulating technique1

Zhenyu Yang1, Ming Wang 2, Wei Xia1
Graduate School of Physical Science and Technology,2 Jiangsu Key Lab on Opto-Electronic Technology,
Nanjing Normal University, Nanjing 210046, P. R. China

1. Introduction

Fig.1. Schematic diagram of the self-mixing interferometer withphase modulation

Fig.2. Photo of experimental setup.

2. Experimental setup and results

200nm
400nm
600nm
800nm
1000nm1200nm
1400nm
1600nm1800nmdisplacement （ nm）

600
400
200

7
MeasuredVibration Amplitude /nm

800

0
-200
-400

Error

6

5

4

3

2

-600
-800

1
200

-1000
0

50

100

150

t（ ms）

200

250

400

300

600
800
1000
1200
1400
Reference Vibration Amplitude /nm

1600

Fig.3. The displacement reconstruction result
Displacement Measurement Result
0.03
Theoretical Result
Average Error

Measurement Point
Linear Fit
Error

100

0.02
20

90

18

80

16

70

14

60

12

50

10

40

8

30

6

20

4

10

2

0.01

Error /nm

Measured Displacement /um

The schematic diagram of the self-mixing interferometer withsinusoidal phase modulation is illustrated in Fig.1. A verticalpolarized measurement light beam emitted by a He-Ne laser
propagated through a various neutral density (ND) filter, an electro-optic modulator (EOM) and then reflected back to the laser
cavity by a movable object, forming the self-mixing effect.
Therefore, laser operations are altered and the self-mixing interference signal is monitored by a photodiode (PD) placed behindthe back mirror of the laser. A sinusoidal phase modulation is
obtained by varying of the optical length between the laser andobject through an electro-optical crystal. The polarization of thelight beam is set parallel to the electro-optically active axis of theEOM. The sinusoidal output of the signal generator is transferredto the EOM and pure sinusoidal modulation with extremely low
insert-loss is generated. The object is fixed on a commercial PZT
which can obtain displacement accuracy of 1 nm. When the signal processing unit sends a signal to the PZT controller, the object is moved a measured displacement ΔL. The output signal of
PD is fed into the signal processing unit to retrieve the measured
displacement in real time. To evaluate its performance, the sinusoidal phase modulating self-mixing interferometer was developed as shown in Fig.2. a commercial heterodyne interferometer (5529A, Agilent Co., USA) with 1 nm resolution was used
to test the displacement of the same object for comparison. Fig. 3
show that the displacement reconstruction result of PZT withfrequency 10HZ and amplitude from 200 nm to 1800 nm, themaximum error is 8nm. Fig. 4(a) show that Single displacement
measurement results, the maximum error is 18nm. Fig.4(b) showthat Times average displacement measurement results, the maximum error is 12 nm.

8

1000

error /nm

The principle of self-mixing interference (SMI) is a newmeasuring technique which is applied in interferometry since
1980’s. When a portion of light emitted from a laser source isreflected or scattered back into the laser cavity by an external
target, the reflected light will mix with the light inside the cavity,
causing a modulation of the laser output power. The self-mixing
interference comes from the optical feedback effect. People
always tried to eliminate the optical feedback effect previously.
Gradually people began to make use of it actively to measuresome physical quantities, thus self-mixing interferencetechnology was brought forth. Compared with conventional
interferometers,
self-mixing
interferometer(SMI)
ischaracterized by its capability of high performance with
inexpensive experimental setup and an extremely simple and thepotential in direct industrial applications for vibration anddisplacement sensing. The SMI is well adapted for displacement
measurement of these micro structure devices where cooperative
target like triple mirror retro-reflector target necessitated in someinterferometers is not available.

0

-0.01

-0.02

-0.03
0

0
0

10

20

30
40
50
60
70
Reference Displacement /um

80

90

100

0

10

20

30
40
50
60
70
Reference Displacement /um

80

90

(a)
(b)
Fig.4 Single displacement measurement results and times average displacement measurement results

Conclusion
The numerical simulation and experimental results show thatthe proposed new method can effectively demodulate the phaseof the interference signal with high accuracy of less than 20 nm.
Self-mixing interferometer (SMI) is characterized by its capability of high performance with an extremely simple and inexpensive experimental setup and the potential in direct industrial applications for vibration and displacement sensing .

References[1] W. Ming, et al, Optics & Laser Techno. 33(6), 409-416(2001).
[2] D. Guo, et al., Opt. Express, 13, 1537-1543(2005).

100

1800