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Introduction Telecom providers are serving more and more customers at a higher rate. Large-scale network facilities require longer cable connections between systems. Since most systems use copper cables for interconnection, long distances between systems will cause problems. Longer copper cables will limit the maximum data transmission rate.
These problems can be solved in the optical fiber system or by installing repeaters on existing cables. There are certain advantages in solving these problems in fiber optic systems, but the cost is high. Adding a repeater to an existing link is a simple, effective, and cost-effective solution that does not require replacement of existing equipment.
When designing products designed for telecommunication systems, certain design principles need to be followed. It is very important to maintain the integrity of high-speed interconnected data signals to avoid bit errors. Telecommunication equipment has limited space, so it is very important that the device does not take up extra space. Easy-to-use and easy-to-configure devices will reduce problems caused by user error. All the above principles were considered when designing the repeater circuit.
The main component of the repeater is Maxim's DS3150 T3 / E3 / STS-1 line interface unit (LIU). The device is used to implement all functions from the physical layer to the DS3, E3 and STS-1 line interfaces. The receiver performs functions such as clock and data recovery, signal decoding, and signal loss detection. The transmitter completes the signal encoding and drives the standard compatible signal to a 75Ω coaxial cable. In addition, a built-in jitter attenuator is also used, which can be mapped to the receive or transmit path. Other components include oscillators, passive devices, and external or on-board 3.3V power supplies.
The following figure and table list all the components needed to build a repeater circuit card, but not including the power supply. The circuit is simple and clear. The two DS3150 devices are connected back to back between RPOS / RNEG / RCLK and TPOS / TNEG / TCLK. In this way, it is easy to configure and reduces the probability of installation errors. The following options are available: Remote loopback enable / disable operating mode selection T3 / E3 / STS-1 transmission mode selection long-range / short-range These options are set by switches on the card. For oscillator configuration options, one oscillator can be used for single mode operation, or multiple oscillators can be used for dual mode and triple mode operation. The other components are the magnetic components used for the line interface, and the physical connectors used for the transmission and reception cables. 
Figure 1. T3 / E3 / STS-1 repeater structure diagram
Table 1. T3 / E3 / STS-1 repeater element list Device Part Count DescripTIon Vendor DS3150 2 3.3 Volt DS3 / E3 / STS-1 Line Interface Unit Maxim PE-65968 4 6 Pin SMT 1: 2CT Transformer Pulse Engineering NTH089AA3-34.2680 1 34.368MHz Oscillator 3.3 Volt Saronix NTH089AA3-44.7360 44.736MHz Oscillator 3.3 Volt Saronix NTH089AA3-51.8400 51.840MHz Oscillator 3.3 Volt Saronix BNC Plug 4 Various DIP Switch 1 Various Power Connector 1 Various Resistor Various Capacitor Various led 3 Power & LOS IndicaTIon Various
T3 / E3 / STS-1 low cost repeater
Important: Telecom providers are serving more and more customers at a higher rate. They need larger-scale network facilities, and the length of interconnected cables between systems is also extended. Considering the price advantage, the system interconnection generally uses copper cables, but as the distance and data rate increase, it brings some problems. After these problems were transferred to the optical fiber system, the system cost increased. An alternative solution is to install repeaters, which are cost-effective and do not require replacement of existing equipment. This application note describes a simple low-cost repeater.