How can you remove the empty layers from drawing file?

Type LAYDEL on the command line

Type N

Type the name of layer you want to remove

to remove unwanted layers

type "purge'" in comment 

The layers can be removed only whan the object resides in the layers will be removed,once it is removed it is an empty layer. The empty layers can't be deleted by purge. It might be because the layer is frozen on a viewport or referenced by an object in a block definition. By using EXPORT command it is possible to remove the layer from drawing, which results in creating a DXF file of the drawing. you can edit the dxf file in a text editor and rename all the instances of layers in the file, except the layer deinition.

The easiest way is to use the PURGE command. The command will inventory all unused named objects like layers, blocks, dimension styles, groups, line types and text styles; and the annoying things we can't see like zero-length geometry and empty text objects. From the inventory/dialog box, you may select "layers" for purging/deletion.

The easiest way to do get rid of empty layers is to purge them. The Purge command will not only remove unused layers but can also remove unused block definitions, dimension styles groups linetypes and text styles. It can be found under drawing utilities or can be executed by simply typing purge. Please click on the following link for a detailed step by step procedure for using this command. 

https://knowledge.autodesk.com/support/autocad/learn-explore/caas/CloudHelp/cloudhelp//ENU/AutoCAD-Core/files/GUID-FEDE9BD6-EA-BE-A5EFB6CAFE-htm.html