Darja Cirjulina, Zhuoyan Zhang, Abdul Hayee, Armands Ostrovskis, Richard Schatz, Hamza Dely, Yan-Ting Sun, Toms Salgals, Sandis Spolitis, Vjaceslavs Bobrovs, Lu Zhang, Djamal Gacemi, Angela Vasanelli, Carlo Sirtori, Xianbin Yu, Oskars Ozolins, Xiaodan Pang
{"title":"Mid-Infrared Free-Space Optical Communications: Technologies, Demonstrations and Future Directions","authors":"Darja Cirjulina, Zhuoyan Zhang, Abdul Hayee, Armands Ostrovskis, Richard Schatz, Hamza Dely, Yan-Ting Sun, Toms Salgals, Sandis Spolitis, Vjaceslavs Bobrovs, Lu Zhang, Djamal Gacemi, Angela Vasanelli, Carlo Sirtori, Xianbin Yu, Oskars Ozolins, Xiaodan Pang","doi":"10.1049/ote2.70034","DOIUrl":"https://doi.org/10.1049/ote2.70034","url":null,"abstract":"<p>Free-space optical (FSO) communication is rapidly advancing as a high-capacity wireless technology, with growing interest in extending its operation from the traditional near-infrared to the mid-infrared (mid-IR) spectral region. Particularly, the mid-wave infrared (MWIR) and long-wave infrared (LWIR) atmospheric transmission windows in the mid-IR region provide advantages regarding reduced turbulence effects, scattering and absorption, enabling more robust links under adverse conditions. This review presents recent progress in MWIR and LWIR FSO communication systems, highlighting advances in transmitter and receiver technologies, such as quantum cascade lasers (QCLs), lithium niobate modulators and detectors, including quantum cascade detectors (QCDs), mercury cadmium telluride (HgCdTe and MCT) photodiodes and quantum-well infrared photodetectors (QWIPs). Experimental demonstrations achieving multigigabit to tens-of-gigabit data rates with advanced modulation formats, digital equalisation and coherent detection are summarised. The paper discusses integration trends in MWIR and LWIR photonics, coherent communication strategies and hybrid FSO–radio frequency (RF) architectures. Together, these developments outline the pathway for MWIR and LWIR FSO systems to evolve from laboratory demonstrations towards scalable, practical platforms for next-generation terrestrial and space communication networks.</p>","PeriodicalId":13408,"journal":{"name":"Iet Optoelectronics","volume":"20 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/ote2.70034","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147668224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Enhanced Four-Wave Mixing From 1.55 to 2.05 μm Enabled by a Black Phosphorus-Based Highly Nonlinear Microfiber for All-Optical Wavelength Conversion","authors":"Lu Sui, Zidong Zhou, Wanzhuo Ma, Huan Wang","doi":"10.1049/ote2.70032","DOIUrl":"https://doi.org/10.1049/ote2.70032","url":null,"abstract":"<p>All-optical wavelength conversion (AOWC) is essential for overcoming wavelength blocking in wavelength-division multiplexing systems and improving bandwidth utilization. Integrating two-dimensional materials with optical microfibers presents a promising route to enhance nonlinear performance. Here, we demonstrate an efficient AOWC device based on black phosphorus (BP)-deposited highly nonlinear microfiber, which operates through the four-wave mixing (FWM) process. The converter achieves a conversion efficiency of −33.51 dB at 2.05 μm. Systematic characterisation reveals that the efficiency increases by 4.56 dB as the pump power rises from 1.83 to 2.00 mW, whereas it decreases by 16.76 dB when the signal–pump wavelength spacing broadens from 3.5 to 11 nm, consistent with FWM power dependence and phase-matching constraints. The device also exhibits excellent stability, with power fluctuation within ± 1.08 dB over 140 min. This work provides valuable insights into the nonlinear coupling between 2D materials and microfibers, supporting the development of practical low-power high-speed all-optical signal processing systems.</p>","PeriodicalId":13408,"journal":{"name":"Iet Optoelectronics","volume":"20 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/ote2.70032","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147668102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"NLUNet: A Novel Approach for Optical Coherence Tomography Images Enhancement via Deep Learning","authors":"Ahmadreza Mohammadi, Mohammadreza Hassanzadeh, Seyedreza Abdollahi","doi":"10.1049/ote2.70027","DOIUrl":"https://doi.org/10.1049/ote2.70027","url":null,"abstract":"<p>Speckle noise significantly reduces the quality of optical coherence tomography (OCT) images. In this paper, two new methods, SRUNet and NLUNet, are introduced to enhance OCT images and reduce speckle noise. These methods are developed based on deep learning and a conventional image processing technique while operating without ground truth images. In the SRUNet method, a combination of UNet and ResNet architectures is used, so that the UNet encoder section is combined with ResNet to reduce speckle noise and recover structural details with significant accuracy. In the NLUNet method, the UNet architecture combined with a nonlocal mean filter (used as a post-processing) resulted in the removal of speckle noise and improved image resolution. These two methods were evaluated using PSNR, SSI and MSE metrics. The measured values of PSNR, SSIM and MSE were 28.88, 0.76 and 84.05, respectively. The results demonstrate that the NLUNet method performs properly to reduce the noise and improve the image quality.</p>","PeriodicalId":13408,"journal":{"name":"Iet Optoelectronics","volume":"20 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/ote2.70027","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147666169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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