Optical true time delay technique with bidirectional consistency based on unidirectional optical amplifier

Abstract

The insertion loss of the optical true time delay line is mainly composed of optical waveguide transmission loss, optical switch loss and input-output coupling loss. When the insertion loss is large, the optical power needs to be compensated by the optical amplifier. In order to realize bidirectional optical amplification of true time delay line and ensure high consistency of bidirectional link performance, a new scheme of optical delay line based on unidirectional optical amplifier multiplexing is proposed. Different from the traditional bidirectional delay line that requires one optical amplifier in each of the uplink and downlink, the scheme proposed in this paper reuses the same optical amplifier in the two-way links. As a consequence, the number of devices employed is halved, and the pressures on circuit layout, power consumption and heat dissipation are also reduced. Furthermore, it solves the problem of large performance differences in insertion loss, gain, and optical noise, etc. caused by the opposite experience of optical bidirectional transmission in traditional links. In addition, the scheme in this paper also avoids the problem of performance degradation that may be caused by the use of bidirectional optical amplifiers and other devices with high complexity. In a typical circuit of two-stage cascaded optical delay line, the optical amplifier is placed between the two stages. Through the scheme of unidirectional optical amplifier multiplexing, the bidirectional differences of insertion loss, gain of the optical amplifier and the optical noise are reduced by about 4dB.