It is desirable to establish affordable smart networks with high speed and low latency for various 5G/F5G applications, which can now be realized by the implementation of cost-effective 10Gbps/25Gbps narrow band DBR EMLs. China Unicom has proposed a Dense Wavelength Division Multiplexing (DWDM) 5G smart network scheme based on 10/25 Gbps tunable lasers, which is known as the ITU-T G.698.4 standard. This paper presents thorough experimental evaluations on a couple of high speed narrow band DBR EMLs, i.e. narrow band DBR lasers with integrated electroabsorption modulators (EAMs), which were XMD box packaged from OptoChip Optoelectronic Ltd. Test results have established that these DBR EMLs have met all of the specifications for a 10Gbps tunable module SFP+, defined by the ITU-T G.698.4 standard, meanwhile they have also met the majority of the specifications for a 25 Gbps tunable module SFP28, defined by the ITU-T G.698.4. They may also be suitable for the implementation of the NG-PON2 networks in USA. The successful development of cost-effective high speed and low latency 10/25 Gbps narrow band DBR EML tunable module SFP+/SFP28 has paved the way towards the wide implementations of various cost-effective, reliable, high speed and low latency smart networks, which may further induce various innovative technologies based emerging industries worldwide.