I. Introduction
Protection of modern computer networks from electromagnetic interference is an important issue. Much attention is paid to the susceptibility to the effects of powerful ultrashort pulses (USP) - nanosecond and subnanosecond pulses. [1]. The use of known protection devices [2] for solving this problem is complicated by a number of conflicting requirements, for example, low mass and high reliability. In addition, USPs are able to penetrate various pieces of equipment, bypassing the instrument screens. The possibility of protection using modal filtering devices is known [3].