en Railway track and structures Railway track and structures پژوهشي Research Today, huge amounts of data are transmitted around the world through the high capacity of the optical telecommunication networks. In railways, optical transmission networks play an important role in transmitting vital rail data too. Improving the reliability of telecommunication infrastructures is essential to increase productivity, maintain traffic safety and reduce maintenance costs. In this paper, first the reliability of the optical transmission telecommunication network has been modeled and calculated analytically through RBD method and then its results have been approved through Monte Carlo simulation. Due to the importance of the optical transmission network in railway safety, the probability of optical transmission network outages and the Mean Time between Failure (MTBF) for 3 years have been calculated and simulated. A case study for this research was performed by using the real breakdown statistics of the network based on the optical telecommunications of the high-traffic railway area in "Azerbaijan District”, one of Iranian Railways network in north-west of Iran. Reliability, RBD model, MTBF, Railway Optical Transmission, Network, Monte Carlo Simulation 15 24 http://ijrare.iust.ac.ir/browse.php?a_code=A-10-228-2&slc_lang=en&sid=1 Maziar Yazdani yazdani_maziar@yahoo.com 180031947532846002559 180031947532846002559 Yes Railway Technical & Infrastructure Dept, Tehran, Iran Railway Technical & Infrastructure Dept, Tehran, Iran Fatemeh Hajizadeh fahajizadeh@hotmail.com 180031947532846002560 180031947532846002560 No 1Railway Technical & Infrastructure Dept, Tehran, Iran 1Railway Technical & Infrastructure Dept, Tehran, Iran Saeed Ghazi Maghrebi S_ghazi2002@yahoo.com 180031947532846002561 180031947532846002561 No Department of Communications, Islamic Azad University, Yadegar-e-Imam Khomeini (RAH) Shahr-e-Rey Branch, Tehran, Iran Department of Communications, Islamic Azad University, Yadegar-e-Imam Khomeini (RAH) Shahr-e-Rey Branch, Tehran, Iran Mohammad Ali Afshar Kazemi dr.mafshar@gmail.com 180031947532846002562 180031947532846002562 No Department of Management, Islamic Azad University, Qeshm Branch Department of Management, Islamic Azad University, Qeshm Branch