In this paper we report the splicing losses of a single mode optical fiber at different humid conditions and at different places of Bangladesh Railway West Zone (BRWZ). The location of the splicing points and their losses for a single mode step index optical fiber have been measured by optical time domain reflectometer before re-splicing. Fusion splicer is used to re-splice these points at different humid conditions to analyze the splicing loss dependency. From this study it has been found that different humid conditions affect the splicing losses to a large extent.

During the second half of the twentieth century there were several technological revolutions around the world, one of the most important being the supplanting of telecommunication over copper wires by optical transmission over glass fibers. Advances in optical fiber technology have been spectacular in the past 30 years but still there is more to come. Photonic fiber structures will create a radically new era of fiber optic communication. In this paper the rapid growth of optical fiber technology is reviewed and its possible new directions in communication are discussed.

In this paper we studied the dispersion and loss characteristics of several types of optical fiber through a simulation study. The single mode step index optical fiber is the best road for a minimum dispersion. Using single mode step index fiber with proper profile the minimum dispersion and minimum loss is obtained at 1550 nm wavelength. Thus data with extremely high bandwidth can be transmitted to an enormous distance through it without any repeater or amplifier with minimum loss and dispersion.

Background : Avascular necrosis (AVN), also known as osteonecrosis of femoral head is a pathology in which many etiologies play role and cause decreased vascular supply to subchondral bone of femoral head which results in osteocyte death. MRI is the most sensitive modality for detection of AVN and is helpful for screening and detecting at early stage. Purpose: The aim of the study was to determine the prevalence pattern and stages of presentation of Avascular Necrosis (AVN) of the femoral head. Materials and Methods: This was a retrospective study carried out at the department of Radiology & Imaging, National Institute of Traumatology & Orthopedic Rehabilitation (NITOR), Dhaka where MRI of the hip joint was performed during our study period, only those patients which showed positive signs for avascular necrosis of femoral head were included and were analysed over a period of five years. The age, sex, laterally distribution, causative factors, staging according to Ficat and Arlet classification was done. Results: It was found that most commonly males of productive age group (21 to 40 years) were affected. Though most of them had unilateral involvement however number of bilateral cases were also significant. Mostly, patient presented with stage-IV disease accounting for 104 out of 152 patients (68.42%). Conclusion: Considering that the young males were commonly affected and presented with advanced stage disease at the time of diagnosis, it was recommended that screening MRI should be done in all patients presenting with hip complaints. Sir Salimullah Med Coll J 2022; 30: 180-185

Introduction: The prostate is an accessory gland of the male reproductive system. It can be involved by a number of diseases ranging from inflammation to malignant diseases. Most common causes of prostatomegaly are benign prostatic hyperplasia, prostatitis, intraprostatic and periprostatic cyst, prostatic adenocarcinoma. Objectives: To evaluate the diagnostic usefulness of Transabdominal ultrasonography in enlarged prostate and compare the USG findings with the histopathological findings. Method: This cross sectional study was carried out in Radiology and Imaging Department of Sir Salimullah medical college and Mitford hospital, Dhaka, from January 2014 to December 2015 with clinically suspected enlarged prostate by department of Urology and referred to the Radiology and Imaging Department for proper evaluation whether benign or malignant by Trans-abdominal ultrasonography before treatment planning and further management. Results: In this study, mean age was 65. 8 years with standard deviation of mean ± 9. 7 years and the age ranged from 50 to 89 years. The most common symptoms associated with enlarged prostate were incomplete emptying 90%, frequency 84%, intermittency 80% urgency, 76%, weak stream, 70% straining 66%, nocturia 60%. Out of 50 patients, histopathological diagnosis of 44 (88%) was nodular hyperplasia, 2 (4%) was nodular hyperplasia with chronic prostatitis and rest of 4(8%) was adenocarcinoma of prostate. Conclusion: Ultrasonography is a non-invasive, available, radiation free procedure, which is used as a first line preliminary diagnostic procedure.