Packaging And Linewidth Narrowing Technologies Of Tunable V-Cavity Laser

With the further development of optical communication industry,many new applications put forward higher requirements for optical devices.Alone with the development of Dense wavelength division multiplexing(DWDM),fixed wavelength laser's disadvantages gradually emerged.Firstly,the number of fixed wavelength lasers may reach hundreds.As for the applications that need to provide protection of the system,each wavelength needs backup which cause the number of single wavelength lasers become too large.In such situation,the cost can not be afforded,and the complexity of management is also very high.In addition,tunable lasers become more important in these applications such as automatic wavelength configuration,wavelength conversion and wavelength routing.Especially,linewidth of the tunable lasers should be improved in some high order modulation transmission system,such as QPSK,16QAM,64QAM and so on.In this paper,we first introduce the basic characteristics of the semiconductor tunable V-cavity laser(VCL).Then we present a careful study of the feasibility of TO package with this VCL,and a detailed analysis of the factors affecting the optical path and its coupling efficiency.In addition,the high frequency transmission,heat dissipation and device structure technology is introduced.We realize the first tunable laser packaged in a TO device.This greatly reduces the size and cost of tunable laser packaging products,which provides conditions of tunable lasers using in the access network.Then we introduce a detailed analysis of the VCL laser chip encapsulation scheme for small BOX products.The size of this product is just 1/10 the level of conventional tunable laser devices which using the butterfly package,and the cost is still greatly improved compare to conventional tunable decives.In addition,this type of packaging design can be more easy to get high performance than TO packaging.This paper also analyze the influencing factors of optics propagation and coupling efficiency,and compare the tolerance problem between single lens TO packaging and dual lens BOX packaging,which get an important reason for low coupling efficiency of TO devices.In addition,the high frequency transmission,heat dissipation and structure process are also analyzed.On the basis of BOX packaging products,we complete a product design which contains the wavelength locking function.In this design,we analysis a tilt optical path considering the limited space condition.The coupling efficiency of such tilt optical path is just lower than the normal coaxial position design.As for the linewidth compression,this paper also puts forward a optical fiber feedback method to reduce the linewidth which follow the principle of optical feedback.We use a coupler to realize the separation of optical output and optical feedback.One branch of the coupler is used as optical output,while the other one connected the coated optical fiber to achieve full feedback optical power.We compared the effects of various factors to the linewidth.Under the experimental conditions,we find the feedback power and the length of the feedback fiber do the most important impact to laser linewidth,which can be used to realize linewidth compression.We finally realize the laser linewidth to reach 60KHz,which provides the premise application in coherent communication and high order modulation etc..Finally,this paper summarizes the achievements and prospects of the VCL tunable laser product application prospects.