Wind measurement radar system components of the laser AOM balance detector and acquisition card
Wind measurement lidar uses laser as the detection medium, which can interact with tiny particles in the air and has the advantages of high spatial and temporal resolution, high automation, simple installation and easy maintenance, etc.
The basic principle of wind measurement lidar is that the signal light generated by the fiber laser is emitted into the air to be measured through the optical antenna and scanning mechanism, and the pulsed laser interacts with the aerosol particles in the atmosphere to produce the backscattered signal carrying its velocity information, the schematic diagram is as follows.
Table of system components for wind measurement radar
| Image | Name | Description |
| Image1 | ultra-narrow linewidth laser | ultra-narrow linewidth laser 3k 1550nm |
| Image2 | Acousto-Optic Modulator | 1550nm Fibre-Coupled Acousto-Optic Modulator 80Mhz |
| Image2 | Balanced Detector | 1550nm BPD465C-200M Bandwidth 200M, 400M Fibre-Coupled |
| Image3 | DAQ | 250MSps DAQ Module，Pulse trigger output |
Laser for wind measurement radar
Most wind measurement lidars use 1550nm narrow linewidth lasers as the emission source.
The corresponding products from YB Photonics are:
ultra-narrow linewidth laser 3k 1550nm https://www.ybphotonics.com/product/18
Product parameters
| Item | Minimum | Typical | Maximum | Unit | Remark |
|---|---|---|---|---|---|
| Wavelength | 1530 | 1550 | 1570 | nm | Customizable |
| Output power | 10 | 13 | dbm | Customizable | |
| RIN | -150 | dbc/Hz@100kHz | Customizable | ||
| Operating current | 400 | 2000 | mA | ||
| Operating voltage | 4.75 | 5 | 5.25 | V | |
| Side-touch inhibition ratio | 60 | dB | |||
| Extinction ratio | 20 | dB | |||
| Frequency drift rate | 1 | Hz/s | |||
| Wavelength drift | ±15 | pm | 全温 | ||
| Power stability | ±2% | 全温 | |||
| Operating temperature | -40 | ±2% | 70 | ℃ | |
| Storage temperature | -40 | ±2% | 85 | ℃ |
| Line width & noise | Level 1 | Level 2 | Level 3 | Unit |
|---|---|---|---|---|
| Integral line width | 10 | 5 | 3 | kHz |
| Instantaneous line width | 1..17 | 0.78 | 0.32 | kHz |
| Optical noise@10Hz | 7E+06 | 1E+06 | 7E+05 | Hzrms^2/Hz |
| Optical noise@200Hz | 7E+04 | 2E+04 | 6E+03 | Hzrms^2/Hz |
Acousto-Optical Modulator (AOM) for wind measurement radar
The acousto-optical modulator parameters of the laser wind measurement radar are: 1550nm, 80M shift frequency, fiber optic input coupling. the corresponding products of YB Photonics are:
https://www.ybphotonics.com/product/21
| Parameter | Unit | Min | Max | Typical | Comments |
|---|---|---|---|---|---|
| Material | TeO2 | ||||
| Wavelength | nm | 1520 | 1580 | 1550 | |
| Average optical power handling | W | 0.5 | |||
| Peak (pulse) optical power handling | W | 0.5 | |||
| Ultrasonic Velocity | m/s | 4200 | |||
| Insertion Loss | B | 3 | 2.5 | ||
| Extinction Ratio (1st order on / off) | B | 50 | |||
| Return Loss (RF ON) | B | 40 | |||
| Rise-time / Fall-time: (10% - 90%) | ns | 30 | |||
| Frequency | MHz | 80 | |||
| Frequency Shift | MHz | +80 | |||
| Radio Frequency Power | W | 2.5 | |||
| VSWR | 1.2:1 | ||||
| Input Impedance | Ω | 50 | |||
| Device Interface | SMA | ||||
| Fibre Type | SMF-28e | ||||
| Fibre Length | m | 1 | |||
| Fibre Termination | FC/APC | ||||
| Working temperature | C | -20~60 | |||
| Storage Temperature | C | -30~70 |
Balance detector for wind measurement radar
Wind measurement lidar usually uses a balanced detector, for 1550nm fiber input, common mode rejection ratio > 25db; bandwidth for there are 200M, 400M bandwidth, the corresponding products are：
https://www.ybphotonics.com/product/13
| Item | BPD465C-10M | BPD465C-75M | BPD465C-200M | BPD465C-400M | BPD465C-DAS-200M |
|---|---|---|---|---|---|
| Materials | InGaAs/PIN | InGaAs/PIN | InGaAs/PIN | InGaAs/PIN | InGaAs/PIN |
| Wavelength | 800-1700nm | 800-1700nm | 800-1700nm | 800-1700nm | 800-1700nm |
| Input Connector | FC/APC | FC/APC | FC/APC | FC/APC | FC/APC |
| Responsiveness | 0.9A/W @ 1550 nm | 0.9A/W @ 1550 nm | 0.9A/W @ 1550 nm | 0.9A/W @ 1550 nm | 0.9A/W @ 1550 nm |
| Common mode rejection ratio | >26dB | >25dB | >25dB | >25dB | >25dB |
| RF Bandwidth | DC-10MHz | DC-75MHz | DC-200MHz | DC-400MHz | DC-200MHz |
| RF rise time @50Ω load | 40ns | 5ns | 1.8ns | 1.0ns | 1.8ns |
| RF Gain | 300kV/A | 88.5kV/A | 18.3kV/A | 4.5kV/A | 80kV/A |
| Minimum optical power@1550nm | -54.2dBm (3.76nw) | -39.0dBm (0.13uw) | -33dBm (0.5uw) | -29dBm (1.25uw) | -35dBm (0.32uw) |
| Saturated optical power@1550nm | -22dBm (6.25uw) | -14.2dBm (37.6uw) | -7.4dBm (180uw) | -1.36dBm (730uw) | -15.6dBm (27.8uw) |
| Noise voltage@50Ω | <18mVpp | <20mVpp | <18mVpp | <10mVpp | <30mVpp |
| RF Output Impedance | 50Ω | 50Ω | 50Ω | 50Ω | 50Ω |
| RF output swing @50Ω load | ±2.0V | ±2.0V | ±2.0V | ±2.0V | ±1.0V |
| Work Voltage | 12VDC ±10% | 12VDC ±10% | 12VDC ±10% | 12VDC ±10% | 12VDC ±10% |
| Work current | <200mA | <200mA | <200mA | <200mA | <200mA |
| Output connector | SMA | SMA | SMA | SMA | SMA |
| Work temperature | -20~65℃ | -20~65℃ | -20~65℃ | -20~65℃ | -20~65℃ |
| Storage temperature | -40~85℃ | -40~85℃ | -40~85℃ | -40~85℃ | -40~85℃ |
| Dimension | 90mm x 60mm x 22mm | 90mm x 60mm x 22mm | 90mm x 60mm x 22mm | 90mm x 60mm x 22mm | 90mm x 60mm x 22mm |
Acquisition card for wind measurement radar
Data acquisition card for LIDAR, when we choose 80M acousto-optic modulator for signal modulation, the acquisition card we can choose the sampling rate of 250MSps, which is a data acquisition card developed for LIDAR application with built-in pulse output and then signal acquisition. Product parameters are:
https://www.ybphotonics.com/product/25
- 14bits dual-channel simultaneous real-time sampling
- 100MSps sampling rate
- DC coupling, 50Ω input impedance
- 2Vpp input voltage range, 0-60MHz analog bandwidth
- Up to 88dBc SFDR
- Trigger output pulse, 16-channel digital IO
- PCI Express x8 Lane high-speed transfer interface
- 2GB DDR3 cache
- Built-in fiber optic sensing and demodulation algorithm