A cost-effective 25 Gb/s directly-modulated transmitter optical sub-assembly (TOSA) packaging solutions by transistor outline (TO)-Can materials and processes were proposed and demonstrated. The purpose of this dissertation is to develop a high bandwidth TO-Can header for high-speed laser module, to verify a method, to propose a three-version of 25 Gb/s TO-Can laser module packaging, and to analyze in the frequency-domain and time-domain, and to experimentally demonstrate a 25 Gb/s TOSA. Usually, the transmission bandwidth of a conventional TO-Can laser module is limited below 10 GHz. To overcome this limitation and figure out the solution, firstly, the geometric structure of a conventional TO-56 header was analyzed by using transmission line models and electrical characteristics of the TO-56 header through a three-dimensional electromagnetism full-wave simulation software. The simulated results were in good agreement with the measured results and verify the applicability. Furthermore, we found that the 3-dB bandwidth of a conventional TO-56 header was limited at 16.7GHz. In this study, the first version of TO-Can header V1 was proposed to overcome the problem of the discontinuous impedance. By applying the TO-Can header V1, a TO-Can laser module package was proposed. The electrical characteristics parameters of the TO-Can header V1 were extracted and combined with small-signal equivalent circuit models of laser diode to simulate the electrical characteristics of the entire TO-Can laser module by the circuit simulation tool. Since bent inside feed-leads and two-step coaxial feed-through holes of the TO-Can header V1 were difficult to achieve in our laboratory equipments, the second version of TO-Can header V2 was proposed and verified experimentally. A 25 Gb/s TO-Can laser module with a matching resistor by adopting the TO-Can header V2 was proposed. The simulated results of this solution by considering with bonding-wires showed that the transmission bandwidth and eye diagram could achieve requirements of 25 Gb/s transmissions. Finally, the third version of 25 Gb/s TO-Can laser module adopted the TO-Can header V2 and an AlN submount of L-shaped microstrip line was proposed, fabricated, and measured. A DFB LD chip with a 3-dB bandwidth of 21.2 GHz was modeled and used in the simulation and the fabrication. Due to the parasitic effect induced by bonding-wires and die-bonding structure, the variation of high frequency performance of the laser module was simulated comprehensively. By referring to the proposed structure, a TOSA was fabricated by a conventional TO-Can and TOSA fabrication equipments and processes. The measured 3-dB bandwidth of the TOSA was 18.7 GHz. A clear eye diagrams of 25 Gb/s and BER testing for BTB and SMF transmission were obtained. This cost-effective solution of the TOSA is compatible with existing automatic TO-Can process lines and can be fabricated massively. Therefore, the results of this study of proposed TOSA can be applied in the next generation networks of 100GBASE-LR4, OTU4, and 32GFC. The presented simulation and verified technique may provide sufficient estimation and step-by-step analysis to assist the high-speed and high-density optical communication applications and various product developments in the future.