18-21th, June, 2018 CLRC 2018, OKINAWA, JAPAN Low Coherence Doppler Lidar with High-Power DFB-LD Tatsuo Shiina, Chiba University, Japan
Inage coast at 20:25 in 24 th Sep. 2015. LED mini-lidar for sea wave motion monitoring at shallow angle Backgrounds
Backgrounds Current Doppler lidar Advantage Disadvantage Compact High-cost Maintenance free Blind area in near range Easy installation Low resolution Strong Demands Near range observation Follow the quick motion Low cost
Purpose Low Coherence Doppler lidar Observation Range Target Wind(Air cell) Off-set range Speed 0.1 – 30 m/s = a few hundred m High-power Low Coherence DFB-LD Low Coherence Doppler Lidar Coherence Length = Spatial Resolution Reference path length can change the off-set distance ( < a few m ) Current Coherence Doppler lidar
High-Power DFB-LD �� � � � ������� �� Low Coherence Doppler lidar DFBLD ������ �������� Specification Output ��������������� Observation Range = Off-set Range ����� a few meter – a few hundred meter � �������� ������ �������� �������� �������� �������������������������������� ᴫ��≉�� ������������ Specification of high-power DFB-LD Output Power ������������������������������������������������ Hamamatsu � ��������� � Photonics ���������������������������������� ＞ 1W Model 976nm DFB-LD � � � ��� Spectral Width [nm] Spatial Resolution � ⥺ᖜᵝணᐃ್ Wavelength 974nm � a few meter 2.7W Output power [CW:max]@3A Coherence Length Spectral Width <14pm � ⥺ᖜᐇຊ್ 1m � Coherence Length 0.1 m Current [A] � ����� ͤ Υ �Ⓨရ�ཧ⪃�ᩱ � ��������������������������������������������� ⣲Ꮚୗ�� Υ � ��ရᵝ��������� ෭༷��ᚲ������� ᵝ��⣙᮰������������ �� ��������������� ��������� ����������������� ����� ���� � �������� ������ �������� � �� ���� � � � � � � ��� ��� ���� � � ��� ����
High-powered DFB-LD �� � � � ������� �� ������ �������� ��������������� ����� � �������� ������ �������� �������� �������� �������������������������������� ᴫ��≉�� ������������ ������������������������������������������������ � ��������� � Output Power Characteristics ���������������������������������� Coherence Length Characteristics � � � ��� Spectral Width [nm] � ⥺ᖜᵝணᐃ್ � Lidar Light Source Operation Forward Current 2A, Temperature 35℃ Optical Output Power 1.76W, � ⥺ᖜᐇຊ್ Coherence Length 0.8m � Current [A] � ����� ͤ Υ �Ⓨရ�ཧ⪃�ᩱ � ��������������������������������������������� ⣲Ꮚୗ�� Υ � ��ရᵝ��������� ෭༷��ᚲ������� ᵝ��⣙᮰������������ �� ��������������� ��������� ����������������� ����� ���� � �������� ������ �������� � �� ���� � � � � � � ��� ��� ���� � � ��� ����
Doppler Shift Observation Fundamental setup of low coherence Doppler lidar Rotation Speed 0.5 – 10 m/s PD BS Target DFB-LD
Doppler Shift Observation Heterodyne Detection Results Velocity estimation Deviation of velocity estimation +/-0.03 m/s
Doppler Shift Observation Diffuse Reflection Plate White Paper Deviation of velocity estimation +/-0.10 m/s
Doppler Shift Observation Second setup of low coherence Doppler lidar Fog Generator 600mm x 450mm Fog Wind Tunnel Compact Setup Target Flowing Mists
Doppler Shift Observation Heterodyne Detection Results Wind Speed observation (Anemometer) Average 0.72 m/s Summation Wind Speed SNR 35s 0.64m/s (1.31MHz) 0.26dB
Lidar Setup Third setup of low coherence Doppler lidar 90mmφ Lidar setup Installation of Telescope Optical fiber interferometer Valance detector
Doppler Shift Observation 0.7nW Heterodyne Detection Results Estimation of minimum detection = maximum distance of 360m
Doppler Shift Observation Diffuse reflection plate Change of reference optical fiber length = control of off-set distance 2m 6.5m Ideally any distance can detect by switching the optical path length Heterodyne Detection Results
Summary Low coherence Doppler lidar is proposed and fabricated as trial approach. Advantage Compact & Low cost 30cm Cube, 1.76W High-resolution 0.8m Maintenance Free LD light source Current status Electrical Design Amplifier & FFT board Design Theoretical Approach Estimation of near range efficiency
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