# The Firmware Design and Implementation Scheme for C Form-Factor Pluggable Optical Transceiver +
## 1 Introduction  
In recent years, the demand for integrated telecommunication networks has increased because of the rapid increase in traffic due to the expansion of information technology devices such as smart devices and intelligent Internet-of-Things devices. The demand for integrated mobile services has also increased through the emergence of 5G technology [1, 2, 3], which enables up to 20 giga bits per second (Gbps) and 1 million units per device and is expected to be approved and commercialized by the International Telecommunication Union as an international standard in February 2020. According to the predicated growth of traffic from 2015 to 2020, it is expected that average annual 26% increase in traffic will cause an increase from 42,372 petabytes (PB) in 2015 to 133,454 PB in 2020 [4]. The role of a high-bandwidth optical transmission network with optical communication technology in the core network area is clearly important [5]. In addition, technology for transmitting 100 Gbps data in optical transmission network has been studied and is a promising solution to this issue [6]. An optical transceiver is a module that converts electrical signals received through routers and switches into optical signals for optical fibers, transmits them, and then converts them back into electrical signals. Optical transceivers, which are commercially used in optical transmission networks, support 100 Gbps using 10 or 25 Gbps transmission rate channels [7, 8], and optical transceivers capable of supporting up to 400 Gbps for next generation optical communication are under development [9, 10]. C form-factor pluggable (CFP) optical transceivers are among the types of optical transceiver used for long-distance data transmission over 100 Gbps. The CFP multi-source agreement (MSA) standard is the industry standard for physical/electrical specifications, control and management practices for quality assurance, and cost savings of CFP manufacturers [11, 12]. The CFP firmware enables communication between the CFP and external host controller communicates the CFP transceiver status through this communication interface, and receives control commands for the CFP transceiver operation. CFP firmware is also responsible for monitoring and controlling the state of the CFP transceiver by configuring the memory and updating the information according to the standard. The firmware designed by existing CFP transceiver manufacturers is based on industry standards, but manufacturers do not disclose their design techniques. Although research on optical transceiver design is actively underway, such as on optic components, printed circuit board (PCB) design [13], and digital signal processor (DSP) chip design for signal modulation [14], there is less research on firmware design technology for CFP transceiver operation. Meanwhile, a micro controller unit (MCU) intergrated circuit (IC) manufacturer has introduced an IC with a basic interface for designing CFP firmware, but it only provides CFP transceiver and host interface functions, rather than a design method for the entire operation of the optical transceiver [15]. Therefore, suitable and optimized firmware technologies are required for developing and improving of the optical transceive. In this paper, we propose a CFP firmware design method based on the MSA standard. By implementing the CFP firmware using the proposed design method, quality can be ensured and cost and development time can be reduced. Meanwhile, digital diagnostic monitoring data is essential information for the host using the optical transceiver. We proposed a high-order polynomials calculation and a temperature calibration method to improve the accuracy of the diagnostic monitoring of optical transceiver. Also, we proposed a memory access method to ensure stable memory access for optical transceiver control and monitoring. In Section 2 of this paper, we describe the derivation of the firmware requirements by analyzing the MSA standard for firmware design.