Antarctic sea ice is a sensitive factor to global climate changing. Study the sea ice changing laws is useful to choose the safe routes for the scientific investigation and merchant ships. South Shetland Islands adjacent sea is an important krill fishing area, it could be beneficial to choose the suitable days and routes to know the sea ice distribution and moving features in fishing seasons in advance. SAR data has the advantage of better penetrating ability than visible and infrared bands remote sensing data, they are more suitable to detect Antarctic sea ice than optical remote sensing data. A series of imagery pre-processing steps were carried out, including heat noise removing, radiometric calibration, speckle filtering, geo-coding, projection transformation, subarea clipping. Threshold method was carried out to detect sea ice, and 24 sea ice distribution maps were gotten from December 2015 to February 2016. Then sea ice concentration were calculated based on the sea ice extraction results maps, and sea ice changing law were analyzed in the South Shetland Islands adjacent sea area. Multi-polarization SAR data is more beneficial to improve the sea ice detection accuracy in the Antarctic sea area.
We propose and demonstrate an auto-bias control scheme for the IQ-modulator of a flexible optical PSK or QAM or other modulation formats transmitter in this paper. Due to IQ-modulators usually producing higher-order modulation format, these modulation formats involve phase mostly. It is based on that the bias drift will change the operating point and result in varying the output optical phase. This technology has no restrictions on modulation formats, so it has good flexibility. The experimental result show the three biases can be stabilized when the proposed scheme is implemented.